[Note: A nice guy emailed to thank me for the following, which I posted to my .NET list in May but forgot to put on the blog, so I'm posting it now; hopefully it will be useful to someone else.]
If you're using v1.1 of the Framework and encounter an SEHException and
have no idea what's causing it, check to see if you called
Application.EnableVisualStyles(). Apparently that is the source for a
number of problems that appear as SEHExceptions.
My problem in particular was happening when I tried to show a form with
ShowDialog(). If I used Show() instead, no problems. All of my other
forms had no problems with ShowDialog, yet this one would crash the app.
After a bit of Googling, it appears that this error can come up almost
anywhere, so keep this in mind as it's almost always the solution.
Interestingly, using a manifest file to get the same results does NOT
cause the app to crash. Go figure.