Sorry for the delay. I did look into some of your questions yesterday, but didn't have any great answers then.
I just tried to load your site and I got a 500 error message with the text:
SQL=INSERT INTO oshowj1_banner_tracks (`count`,`track_type`,`banner_id`,`track_date`) VALUES (1, 1, 10, '2013-04-03 14')
Not sure what's happening there, but it didn't happen again when I reloaded. Just thought I'd let you know.
For the 'f' missing, I'm not seeing that in Chrome or Safari on a Mac. Can you explain more of what you're seeing:
I am seeing the redirect issue when I try to login. Can you tell me what SEF extension you're using? If it's not the built-in Joomla SEF, can you go into it's settings and set it to 'skip' JFBConnect. It's different how to do that in each extension, but hopefully that helps.
If you're using Joomla's SEF, can you try to disable it temporarily?
One final thing to test is going into Global Configuration of Joomla and turning 'off' GZip Compression and set Error Reporting to 'maximum'. That will hopefully provide a better error message which will help us diagnose things.
Thanks,
Alex