I have a problem with a worksheet I've used for many years. Although I recently switched to Excel 2007, this had started to occur a while ago, with Excel 2000.

If I hover on a cell containing a comment, the comment correctly appears next to the cell. But if I right-click and pick Edit Comment, the following happens: screenshot
  • A rectangular group of cells becomes entirely blank, except for red and green triangles.
  • The top-right cell in the blanked area flashes slowly.
  • The comment is nowhere to be seen, and cannot be accessed even if I right-click in the area where it would appear.

I have been unable to find a solution to this problem. Thanks for your help.