System error &H8007007E (-2147024770). The specified module could not be found
 

Did anyone get this error message when running VbA in an Excel Workbook?

Here's how I get it:

I open an Excel 2000 Workbook using Excel XP. The workbook has code in the
Open event. When the workbook opens, I get the error. Then it gives me a
"Insufficient memory" message.
If I hit a button that has code under it, even if I stick a breakpoint at
the very beginning of the sub, I get both errors then it stops at the break
point. If I stop the execution, again there's those two errors.

Any idea what's causing this behavior?

Here' my config:
WinXP with auto-update activated
Office XP Pro
The workbook has been saved with Excel 2000 and it's using
mscomctl2.ocx(I've installed the ocx on Excel 2000 computers)

TIA,