In current module version, there are some uses of the "dimdim_users" table (lib.php) and that table doesn't seem to exist in the module installation file at all.

The most noticeable one is the query in the dimdim_print_recent_activity(), that with debug enabled, displays the error.

Ciao

P.S.: I remember I saw that table in a previous release? Has it been dropped on purpose or by error?