Ok, extremely wierd situation here:

(I'll post the code below, after the explanation)

I've got a Windows application (.NET 3.5) that has a single Form with
a DataGridView embedded.  The user presses a button to do a SQL query
(fill a DataSet).  Before firing the query, I disable the grid/buttons
and turn on UseWaitCursor.  After it completes, I re-enable the grid/
buttons, refresh the dataset, then turn off the UseWaitCursor.  If I
execute this from Visual Studio (in Debug or Release, Run Project or
Manually selecting the executable), it works perfectly fine.  But, if
I run the executable manually (straight from Explorer/Command line),
the application goes into a "Not Responding" mode and never returns.
If I attach the debugger to the process, the line that it gets stuck
on is the grid.Enabled = true.  If I skip that line, it still gets
stuck, but on the BindingSource.ResetBindings(...) call.

I'll post the code below.  Can anyone help me with this?

using System;
using System.ComponentModel;
using System.Configuration;
using System.Windows.Forms;

namespace VAInvoicing
{
    public partial class formMain : Form
    {
        private BackgroundWorker bgWorkerGet;
        private BackgroundWorker bgWorkerSend;

        public formMain()
        {
            InitializeComponent();

            bgWorkerGet = new BackgroundWorker();
            bgWorkerSend = new BackgroundWorker();
            bgWorkerSend.WorkerReportsProgress = true;

            bgWorkerGet.RunWorkerCompleted += new
RunWorkerCompletedEventHandler(bgWorkerGet_RunWorkerCompleted);
            bgWorkerGet.DoWork += new DoWorkEventHandler(bgWorkerGet_DoWork);

            bgWorkerSend.RunWorkerCompleted += new
RunWorkerCompletedEventHandler(bgWorkerSend_RunWorkerCompleted);
            bgWorkerSend.DoWork += new DoWorkEventHandler(bgWorkerSend_DoWork);
            bgWorkerSend.ProgressChanged += new
ProgressChangedEventHandler(bgWorkerSend_ProgressChanged);
        }

        private void formMain_Load(object sender, EventArgs e)
        {
            dtStart.Value = DateTime.Today.AddMonths(-1);
            dtEnd.Value = DateTime.Today;
        }

        private void buttonGetInvoices_Click(object sender, EventArgs e)
        {
            this.UseWaitCursor = true;
            panelFilter.Enabled = panelActions.Enabled = false;
            statusLabel.Text = "Searching for Invoices...";
            progressSend.Style = ProgressBarStyle.Marquee;

            bgWorkerGet.RunWorkerAsync();
        }

        private void bgWorkerGet_DoWork(object sender, DoWorkEventArgs e)
        {
            eqIpaInvoice2TableAdapter.SetCommandTimeout(120);
            eqIpaInvoice2TableAdapter.Fill(eqIpaInvoice2._eqIpaInvoice2,
dtStart.Value, dtEnd.Value,
ConfigurationManager.AppSettings["NameFilter"]);
        }

        private void bgWorkerGet_RunWorkerCompleted(object sender,
RunWorkerCompletedEventArgs e)
        {
            panelFilter.Enabled = panelActions.Enabled = true;
            progressSend.Style = ProgressBarStyle.Blocks;
            progressSend.Value = 0;

            // Refresh the grid and clear selection
            //eqIpaInvoice2BindingSource.ResetBindings(false);
            gridInvoices.AutoResizeColumns();
            gridInvoices.ClearSelection();

            this.UseWaitCursor = false;

            // Did an exception occur?
            if (e.Error != null)
                MessageBox.Show(this, e.Error.GetType().Name + "\n" +
e.Error.Message + "\n\n" + e.Error.StackTrace, "Error!",
MessageBoxButtons.OK, MessageBoxIcon.Error);
        }

        private void buttonSendInvoices_Click(object sender, EventArgs e)
        {
            this.UseWaitCursor = true;
            panelFilter.Enabled = panelActions.Enabled = false;
            statusLabel.Text = "Sending " + gridInvoices.SelectedRows.Count + "
Invoice(s)...";
            progressSend.Value = 0;

            bgWorkerSend.RunWorkerAsync();
        }

        private void bgWorkerSend_DoWork(object sender, DoWorkEventArgs e)
        {
            int success = 0;
            int failed = 0;

            Random r = new Random();
            DataGridViewRow[] rows = new
DataGridViewRow[gridInvoices.SelectedRows.Count];
            gridInvoices.SelectedRows.CopyTo(rows, 0);
            gridInvoices.ClearSelection();

            foreach (DataGridViewRow row in rows)
            {
                // TODO: Do some work here
                System.Threading.Thread.Sleep(1000);

                // DEBUG -- Random number -- 30% failure rate
                if (r.Next(3) != 1)
                {
                    success++;
                    row.ErrorText = "";
                }
                else
                {
                    failed++;
                    row.ErrorText = "[something went wrong]";
                }

                bgWorkerSend.ReportProgress((int)Math.Ceiling((int)(success +
failed) / (double)rows.Length * 100));
            }

            e.Result = success;
        }

        private void bgWorkerSend_ProgressChanged(object sender,
ProgressChangedEventArgs e)
        {
            progressSend.Value = e.ProgressPercentage;
        }

        private void bgWorkerSend_RunWorkerCompleted(object sender,
RunWorkerCompletedEventArgs e)
        {
            panelFilter.Enabled = panelActions.Enabled = true;
            statusLabel.Text = "Sent " + e.Result.ToString() + " Invoice(s)";

            // Make sure buttons are in the correct state
            gridInvoices_SelectionChanged(this, new EventArgs());

            this.UseWaitCursor = false;

            // Did an exception occur?
            if (e.Error != null)
                MessageBox.Show(this, e.Error.GetType().Name + "\n" +
e.Error.Message + "\n\n" + e.Error.StackTrace, "Error!",
MessageBoxButtons.OK, MessageBoxIcon.Error);
        }

        private void gridInvoices_SelectionChanged(object sender, EventArgs
e)
        {
            if (!bgWorkerSend.IsBusy)    // Make sure we're not working on sending
now
            {
                // Show the user how many are selected
                statusLabel.Text = gridInvoices.SelectedRows.Count + " / " +
gridInvoices.Rows.Count + " Invoice(s) Selected";

                // Only enable Send if there are rows selected.
                buttonSendInvoices.Enabled = gridInvoices.SelectedRows.Count > 0;

                // Set the default button (for pressing ENTER)
                if (gridInvoices.SelectedRows.Count > 0)
                    this.AcceptButton = buttonSendInvoices;
                else
                    this.AcceptButton = buttonGetInvoices;
            }
        }
    }
}

And here is the Call Stack for the "locked up" process, the last line
is the last User Code executed (or well, attempting to be executed)
is: panelFilter.Enabled = panelActions.Enabled = gridInvoices.Enabled
= true;

    [Managed to Native Transition]
    System.Windows.Forms.dll!System.Windows.Forms.Control.Update() +
0x72 bytes
    System.Windows.Forms.dll!
System.Windows.Forms.Control.OnEnabledChanged(System.EventArgs e =
{System.EventArgs}) + 0xa7 bytes
    System.Windows.Forms.dll!
System.Windows.Forms.DataGridView.OnEnabledChanged(System.EventArgs e)
+ 0xb bytes
    System.Windows.Forms.dll!
System.Windows.Forms.Control.Enabled.set(bool value) + 0x59 bytes