Could you also go into the Joomla global configuration area and set Error Reporting to Development or Maximum? A blank page usually indicates a PHP error. Both your server error reporting and the global configuration error setting need to be enabled. If you get an error after this, please let me know what it is.
After looking in your administrator area, I'll need FTP credentials to your site to debug this further. There's a call to load configuration from Virtuemart in our Social Profiles plugin that is failing. I've added both VM 2.6.10 and Joomla 2.5.28 to a test site with the latest JFBConnect and am not encountering the same problems. The version of Virtuemart and Joomla you're using are very outdated. Generally, we don't support J2.5 anymore, but I can poke through for a small amount of time if you give me FTP access.