BuddyPress.org

With what you are experiencing, I would image that there is useful information in your server’s log files. How do you locate the log files?

This is a very old article, but perhaps still applies to 1and1:

http://www.devchunks.com/1and1/1and1-hosting-server-logs/

If that does not help, contact them and ask for assistance in locating your log files.