Form converted to .NET 2.0 resizes when rebuilding the project

Today I converted a small project to .NET 2.0.

I had my main form open in the designer when I did a rebuild of the project. The height of my form changed all of a sudden. If I ran my form, the anchoring was completely messed up!

After some testing I removed the MainMenu of my form and the weird behaviour had gone. I had to replace the MainMenu with a MenuStrip...