I may be wrong but I think this happened after I tried to upgrade using the auto upgrade plugin.
I returned to night to find Internal Server Error
I re-uploaded nearly everything except config etc.
I had a look at the db, I don't really know what i'm looking at but I hit the Check and Repair buttons. It said it was all ok.
Isn't it a bit weird I can't even view index.php???
Welcoming any suggestions what might have casued or better still how I go about solving it.