I created a web method which returns void. I then added the OneWay=true
atribute. But the funny thing I noticed is that, even though it is an
async call, the EndWebMethod is called at the end of the execution.

This is what I really want..... I want to call a webmethod and just
totally forget about it. I need nothing in return.

The way I found out that this isn't working is, in my web method I am
doing an insert into the database. This I need to do once and totally
forget about it. But what happens is that, since the EndWebMethod is
called the insert is done again and the database craps out.

Any ideas why??