Sheet not showing

I have an Joomla 2.5 installation and the sheet is not showing anymore, I suspect an PHP upgrade i coursing this?

I get this error: Strict Standards: Only variables should be assigned by reference in /hsphere/local/home/pelargonie/ on line 92

I am running ver.2 and are preparing to migrate to Joomla 3.x but need to back up the data. I have backed up the database in PHPmyadmin can they be used in the Joomla 3.x version.

Best regards Teddy Carlsen