WordPress Automatic Update Fail
I host two WordPress blogs on my hosting plan and the past few upgrades have been a pain in the arse to put it mildly. In simple terms, the "automatic upgrade" failed giving a variety of error messages. One time I was simply having permissions issues; that was a while ago and wasn't a difficult one to fix.
The previous automatic update didn't work, so I did it manually and that worked fine for a little bit, until I got an error message about duplicate header information. After a bit of research I found out that Dreamweaver had inserted a space after one of my php files and it was causing all sorts of havoc.
Now, the most recent update to WordPress 3.0 failed, but I wasn't getting any error message whatsoever, just a frozen screen that said something along the lines of "unpacking core updates...". Finally, I solved the problem...sort of.
I had to delete my wp-content/upgrade folder. I don't know why this happens and would love it if someone does know and can explain it to me, but sometimes WordPress fails to delete the temporary files in your upgrade folder from a previous upgrade. This causes problems. So, all you have to do is go delete that entire folder and try running your update.
I was having some trouble using the automatic update for several plug-ins and that solved those problems as well. Unfortunately, I still have to go delete the upgrade folder myself before doing any automatic updates, but at least that's easy to do and blog life moves forward.
Side Note: It's amazing how much disk space is freed up after deleting the upgrade folder. I did it for both blogs and checked the disk space in CPanel, wow. I highly recommend you do this occasionally.