Not possible to edit Calls

Hello,
We have been using the Sugar CRM (Suite CRM version 7.4, Sugar version 6.5.20 (Build 1001), and lately we can’t edit Calls anymore.
I did a Quick Repair and Rebuild, but it hasn’t changed anything.
We can view the calls, but when we click on Edit, the screen becomes blank.
Can you help?
Thanks,
Kind regards,
Regine

Just an additional information: I could edit a series of calls by using “mass update”.

Hello,
A colleague of mine had the same problem with the Calls and the Meetings as well, so I did a Quick Repair and Rebuild again, and now it works, no need for help any more, sorry for the inconvenience.
Kind regards,
Regine