Glitch with the Minimize/Maximize/Close buttons

This is a bit of a weird one (I'm guessing some kind of file corruption) so I'll do my best to explain...

Excel 2007 / .xlsm workbook

On all worksheets in my workbook, if I hover the mouse over the column headers (or, if they're hidden, the screen space where the column headers would be) directly below the Minimize/Maximize/Close buttons, then each of the buttons will flash rapidly.

Here is a partly mocked up example...

Excel_Glitch01.jpg

The column headers are hidden here, but imagine they are there and the cursor is over them, the same effect occurs.

If the cursor is then moved across slightly, to be vertically underneath one of the other buttons, then that one will flash rapidly instead. It's not a 'uniform' flash either, it's a rapid, intermittent, glitch type flash. It's like Excel thinks the buttons are positioned (where the column headers are) in that screen space. The buttons themselves in the top corner work fine.

It is a macro enabled workbook but I'm not really doing anything remotely complex to cause this. In fact, it seems to affect the whole application as I can open some other non-related workbooks and get the same phenomenon.

Has anyone experienced this before? Hopefully some ideas to save me rebuilding the file from scratch.

Thanks in advance.