One unfortunate side effect of working on a Windows Forms project is that the WinForm designer occasionally loses one or more of your controls. This seems to happen only to C# developers. It appears that this is a well known issue and it is completely maddening when it happens. There you are, carefully crafting you UI, when suddenly the form is empty — all controls gone.
The good news, from Shawn Burke, is that Microsoft has a hot fix available that solves this problem. Plus it is fixed in VS 2005.