DB Error, usernames dropdown list fails to load.

[babe]

Since a month or two, I'm getting the following error on any page that loads the dropdown list with usernames.

DB Error: Bad SQL Query: SELECT user_id, user_name FROM pics_users WHERE user_id <> -1 ORDER BY user_name ASC
Error writing file '/tmp/MYtEnZjj' (Errcode: 28)

The dropdown menu then only lists "Guest" and "--------------------------------", instead of the ten thousands of registered members.

I've searched this forum and learned that error 28 is MySQL-related, but the weird thing is I can't find anything wrong. The tmp-dir isn't even halfway full (which would explain the file writing-error).

I would really appreciate any suggestions to get this fixed.

A fix, eg. how to replace the dropdown list with a simple text entry field, is also very welcome.

[Acidgod]

DB Error: Bad SQL Query: SELECT user_id, user_name FROM pics_users WHERE user_id <> -1 ORDER BY user_name ASC
Error writing file '/tmp/MYtEnZjj' (Errcode: 28)

The mysql User have not rights to write into the Folder or the Partion/HDD is full...