Site-wide theme update issues.

Anyone come across a similar issue as the one below and have a fix?
When I attempt to activate and update a series of themes in the Siteadmin-->Themes section a download dialog comes up asking me to download wpmu-edit.php. Everything else works in my wordpress installation except this. Is anyone else getting this problem? Any ideas for thinking through this one?
(This may have been better served under Theme Support)
Thanks,
Jim