numinix:
FIXED!!!
The problem was because of an IE7 add-in by the company BitComet. All of the computers I tested from have this program installed and disabling it solved the problem. Hopefully not too many customers have this installed.
Glad you got it sorted out on your computers.
Just a reminder that the code has already been rewritten for v1.3.8 to prevent the kind of problems you were mentioning:> DrByte:
Okay ... more information.
If you have javascript support disabled, you'll get the 404 symptoms because the javascript used to do the button-submit won't trigger. This will happen in any browser that has javascript support disabled in some way.
Fortunately, we rewrote all that logic a few months ago in preparation for v1.3.8, and it appears to be fine even in IE7 and with javascript off and on.
So, when v1.3.8 comes out it'll all be grand.
In the meantime, turn your JS support back on.