There it is! A BUG in Visual Basic Express 2010:
I have several ToolStrip controls docked within several panels of a tabPanel.
And sometimes, some toolstrip disappear from the design page.
Still exists since I can see its name in the bottom under the design surface. If I click that name, kazaaaaam!!!, if shows back, but if I click another control elsewhere it vanishes again.
And after compiling and running the project, user can't see it neither.
Only solution is insert a fresh new toolstrip and copy/paste the bad one's buttons!
Any clue?
There appears to be a weird bug in VS2008 and VS2010. For some reason it sets the .Visible property to False. If you go to the Properties section of your Project, select the ToolStrip and then set the .Visible property to True, it should work.