Hi hedera. about the error you might wanna try another browser like Internet Explorer, Firefox, Safari etc.,.
About all of the that was lost, try to check in your database like Phpmyadmin if they're still there. If they do, try to backthem up zip it.
please see http://manual.b2evolution.net/Make_a_backup
and i think you need to upgrade to v. 3.3
Please see http://manual.b2evolution.net/Upgrade_from_an_older_version