[Zope] problems with msie 6

Hi! I'm quite new to zope and I have a little problem with msie 6: I created a formulator form. When it is submitted a python script is called that validates the entries and then calls a zsql method that inserts them in a mysql table. With Mozilla, msie 5.X all works fine, but using msie 6 the entries are inserted two or three times. No error messages appear in the error_log so I have no idea where to look. (Zope version is 2.6.0, formulator version is 1.2.0) Any hints? Thanks in advance Thorsten Harms