I keep getting a "System InvalidOperationException occurred in System Windows Forms dll" error in VB 9.0

I've just started learning VB.NET with VS 9.0; a small application I'm working on keeps returning an "A first chance exception of type System InvalidOperationException occurred in System Windows Forms dll" error from the Immediate Window. The application has almost zero functionality so far, it consists of a menu strip with:

File  About
 |Open
 |Save
 |Save As
 |Quit

The only code I have written opens an Open File dialog, a Sa开发者_运维知识库ve As dialog, an About window with background sound and an OK button, and the Quit button which exits.

Since there is almost no code for me to search through, I can't understand why there would be an error. The program runs just fine when I'm debugging it too.

Strange, when I tried running it again the error wasn't there anymore.