I added various controls to a tiny test application's MXML file in Flash Builder (Gumbo)'s design mode, ran the app, and all was well. Then I opened the file in design mode again, and all I could see was a sea of grey, with no controls visible. When I clicked on a control, a blue border would appear around it, but no other sign of the control was visible. I could drag new controls onto the sea of grey, but they were invisible too.
I have attached a screen shot of the "sea of grey," named "SeaOfGrey.tiff".
What the heck is this? Is there some "sea of grey" mode that I accidentally got into? How do I get out of it?