I decided it was time for a tidy up on one of my blogs. Didn't do anything major, just clicked on a couple of pretty standard plugins to upgrade them - and everything seemed fine. But at the top WordPress was nagging me that v2.9.x was available, so I clicked it. I then chose for it to upgrade automatically and it said everything was fine.
But somehow it had logged me out. I tried to login again and I get: http 500 internal server error.
The website is running OK.
Where do I start to fix this?
Thanking you in anticipation.