Error after login in my forum!

[videogames]

Hello,

When I login I get this error:

Database error in vBulletin 3.7.4:

Invalid SQL:
SELECT userid, usergroupid, IF(displaygroupid=0, usergroupid, displaygroupid) AS displaygroupid, username, posts FROM vb_user ORDER BY posts DESC LIMIT 10;

MySQL Error : Error writing file '/tmp/MYynOhcv' (Errcode: 28)
Error Number : 3
Request Date : Tuesday, October 26th 2010 @ 10:59:33 PM
Error Date : Tuesday, October 26th 2010 @ 10:59:33 PM
Script : http://www.videogames.ir/forums/
Referrer :
IP Address : 79.175.170.181
Username : admin
Classname : vB_Database
MySQL Version : 5.0.91-community


and also No one can login or register ! there is no such this problem before.

I will be very thankful if you help me to solve this problem.

Thanks

[Zachery]

MySQL Error : Got error 28 from table handler

Error Code 28 (No space left on device):
Got error 28 from table handler means your server's mysql partition for your mysql database ran out of disk space or that the /tmp directory ( http://www.mysql.com/doc/T/e/Temporary_files.html )on your server doesn't have enough space, you need to

1. close your forum to prevent further posting or writing to the database
2. contact your web host
3. or if your host yourself on a dedicated server, you need to move your mysql partition to a larger disk or change the /tmp directory location via your servers my.cnf file

[videogames]

Thanks for your very nice and clear answer, My problem has been solved.