Design view of a form missing

[Peter Royle]

I am working with VB.NET. It has just started losing my design view of
a form when I open a project. If the design view was open when I last
closed it, the view is there, but the Solution Explorer doesn't give a
tab for it, and the form in the Solution Explorer just shows as a .vb
file, not as a form icon. To fix it, I have to remove the file from
the project, then re-add it. And once it's gone wrong, it seems to
keep going wrong. Also, it can be only 1 form out of, say, 6 in a
project, that it happens to.

Any ideas??

Peter Royle