I have the same problem,First time I click on the connect button popup window works, and when I click on connect I'm getting this 500 error:
http://www.my-domain.com/component/jfbconnect/?view=xdreceiver&format=raw&fb_login&fname=_opener&guid=0.42870879721115507&session=%7B%22session_key%22%3A%223.C5__y_wpi3yxjPaL4kFNfg__.3600.1270429200-1631478301%22%2C%22uid%22%3A1631478301%2C%22expires%22%3A1270429200%2C%22secret%22%3A%22Iw2bJcSOGhLsOEUG5LTuFg__%22%2C%22sig%22%3A%225fb2e6e9e8c3542b97f2e778eb7960eb%22%7D
If I click on the connect button again, it jumps directly to the 500 error....
Why is it doing this.... everything is done correct, I have even deleted the application, and started over MANY times.. and still this error comes...??
I have those settings in my Joomla configuration:
Search Engine Friendly URLs Yes
Use Apache mod_rewrite Yes
Add suffix to URLs No
I have tested it in both IE and FF, and error comes in both browsers