[Zope] strange form behaviour

[David Kyte]

Hi

I have a form that has a python script as an action
in a plone site. If I login to plone as user admin then the
script works fine. If I login as user djk at microamps.com
the script instead of going to doUpdate as it should,
pops up a dialoge box saying open/save doUpdate.com.

Logging using an email address is fine in all other aspects
and I have been using this with 3000 members for the last year 
just fine. It has just started happening.
 
Anyone experienced anything like that?

TIA

Dave