Every so often when i go to compile my Setup projects, i suddenly get
these errors:

Error    1    Unable to find source file 'C:\...\System.Web.Services.dll'
for assembly 'System.Web.Services.dll', located in '%CE1%\...'    C:\...
\app.vddproj
Error    2    Unable to find source file 'C:\...\microsoft.visualbasic.dll'
for assembly 'microsoft.visualbasic.dll', located in '%CE1%\SWIFT
Mobile'    C:\...\app.vddproj
Error    3    Unable to find source file 'C:\...\mscorlib.dll' for assembly
'mscorlib.dll', located in '%CE1%\SWIFT Mobile'    C:\...\app.vddproj
Error    4    Unable to find source file 'C:\...\System.Data.dll' for
assembly 'System.Data.dll', located in '%CE1%\SWIFT Mobile'    C:\...
\app.vddproj
Error    5    Unable to find source file 'C:\...\System.Windows.Forms.dll'
for assembly 'System.Windows.Forms.dll', located in '%CE1%\SWIFT
Mobile'    C:\...\app.vddproj
Error    6    Unable to find source file 'C:\...
\System.Windows.Forms.DataGrid.dll' for assembly
'System.Windows.Forms.DataGrid.dll', located in '%CE1%\SWIFT Mobile'    C:
\...\app.vddproj
Error    7    Unable to find source file 'C:\...\System.Drawing.dll' for
assembly 'System.Drawing.dll', located in '%CE1%\SWIFT Mobile'    C:\...
\app.vddproj
Error    8    Unable to find source file 'C:\...
\Microsoft.WindowsCE.Forms.dll' for assembly
'Microsoft.WindowsCE.Forms.dll', located in '%CE1%\SWIFT Mobile'    C:\...
\app.vddproj
Error    9    Unable to find source file 'C:\...\System.dll' for assembly
'System.dll', located in '%CE1%\SWIFT Mobile'    C:\...\app.vddproj
Error    10    Unable to find source file 'C:\...\System.Xml.dll' for
assembly 'System.Xml.dll', located in '%CE1%\SWIFT Mobile'    C:\...
\app.vddproj

The only workaround i have found is to create a new setup project from
scratch, which is becoming a serious pain as this happens about every
other day.

Does anyone know what is going on here? How can i fix it without
starting over with the project?