All of the sudden, my Excel 2003 began an odd behavior today. Whenever I click on a worksheet tab that has a PivotTable on it, I become unable to click on any other tabs or on the menu with the options to minimize, maximize, and size at the top left of the worksheet window. I am left unable to click on the other tabs until I double-click inside a cell in the PivotTable worksheet and get a blinking curor as if to type. Then, I can navigate to other tabs normally.

I can't think of any major changes I have made to my computer in the last day that would have caused this. I did instiall PC Tools antivirus over a week ago, and since that time have noticed my computer behaving in odd ways, but excel has been just fine until now.

Does anyone have any thoughts on what might cause this?

Thanks so much.