Windows 7: Problems with Windows7/Office2007 and Tomcat/WebDAV

Hi guys!

I'm desperate :-|

I work for a company and we're delivering a software which runs under Tomcat and uses WebDAV to allow users to edit documents "on-the-fly". Now I'm struggling because one of our customer faces the following problem and I don't know what to do (after searching the Internet for two days):

Our software runs on a test machine and a productive machine. On the test machine a user can upload files but editing with Windows 7/O2007 is not possible. On the productive system it is not even possible to upload files because Tomcat runs into a severe error 500 (Internal Error). I don't know if these problems are linked to each other. But on the other hand they've got a user (from another domain) who can upload and edit on the productive machine.
That's why I first thought about any permissions problems but I couldn't find anything on the Internet about WebDAV restrictions caused by domain policies. Also everything works fine with WindowsXP and Office 2007 so Office isn't the fault actor either.

Here's a short summary:
Test machine:
+ Windows 7: Upload, no editing
+ WinXP: Upload & editing

Productive machine:
+ Windows 7: No upload, no editing
+ WinXP: Upload & editing

I'm really stuck with it because I can't find any error at all? I'm completely out of clues.

Thanks for your help,
bahamut

seems to be a problem with domain policies (our webserver was marked as not trusted)