Matt Nelson wrote:
@tsiak: Have you tried clearing your Joomla cache?
I had exactly the same problem, so I went to "Site -> Maintenance -> Clear Cache". Just clear every thing in there. For me, there were still some files left that would not delete; they were in GantryAdmin. If you have the same problem just SSH or FTP on to your server and delete the files from teh cahce folder of your main install.
Once I had done that I could access the template settings again. Good luck.
Thank you so much for this suggestion, worked like a charm on my Joomla 3.0 website.