I had a similar problem and I thought I'd post how I fixed it.
Every time I logged in I would get a 404 error (page not found) because it would take me to "
http://www.mysite.com//ndex.php" instead of "
http://www.mysite.com/index.php".
The fix was to look inside the configuration.php file in the joomla root directory and remove all the trailing slashes in any references to
http://www.mysite.com. In other words, I changed all instances of "
http://www.mysite.com/" to "
http://www.mysite.com" and all worked fine!
wooHOOO!
