Form[design] tab disappeared

Hi

I tried the 2 listed answers to this problem but neither worked.

I'm writing with VB 2008 Express under .net 3.5

Project going well - no problems until I needed to change the form design again. 

The project still runs OK - the "Form1.vb" and "Form1.Designer" files are still there and look OK, 

BUT the "Form1[design]" tab is missing - how do I get it back?

Deadline approaches - help!!

Thanks in advance

Peter Trueman