discuss.answer
AFAIK I had this one TinyMCE causing that proplem. If you can try to uninstall that extra and see if it works.
Yup that's the fix. I could have sworrrrrrrrrrn I tried it earlier and it didn't work! Achterbahn you rock! Thanks
Glad it helped. Could you mark your question as solved, please.
I have also had this issue several times on different sites after doing an upgrade. Sometimes it is TinyMCE but a few times it has been a plugin called VersionX. Very useful package but caused the blank screen issue described above. Once removed everything was fine and I could reinstall it. Just thought I would post in case anyone else runs into the same issue.