Can not change Account for request

Hi,

I have a request, that a supportRep has opened. But since SupportReps are not contacts, I can not assign them an account.
Our SupportReps in the company can also open tickets for internal request. Therefore I need the account of my own comany associated to the supportReps.
I can edit the request and select the correct account from the dropdown-list. But the request is not saved. Even if I select a different account, it is not saved. Furthermore I can not change the name of the requester. The field is disabled.
I tried to delete the request and created a new one and then I was able to change the values. But of course all conversations and time entries were lost.
It just happened again this morning, that i can not change the account or contact name in a new request.

I use Build 7700

Does anybody have some ideas what to do?

Jürgen