Bug in security update KB936507 Excel 2003 and KB936509 Ex..

I am having a problem with these Excel updates
KB936507 (for Excel 2003) and KB936509 (for Excel 2007)
It affects all version of Excel on every computer that has either update.
The problem is when opening .xls files in an old BIFF5 format (in Excel 2007
[Compatibility mode] is shown in the window title). The spreadsheet grid is
not draw correctly, only the background color is shown, no grid, no
column/row numbers. I can move around the screen with arrow keys and a black
rectangle is drawn around the area where the cell would be, and cell data is
displayed in the input/formula line.
Uninstalling the update solves the problem (so it is certainly a bug) but I
am hoping it could be fixed so my users don't have to disable Automatic
update.
Who can I contact to provide a bug report and example of the problem?
(Customer support refused to take my bug report)