ERROR 1018 (HY000): Can't read dir of '.' (errno: 24)
Upon searching for some solutions at google we found out that the error means 'Too many open files'. Everything you do in linux is a file (or rather a file descriptor). Every mysql connection, every apache connection etc.
To see how many files a user has open try this
sudo lsof -u mysql
edit the file in /etc/security/limits.conf and add these two mysql lines in at the bottom
#@student - maxlogins 4
mysql soft nofile 4096
mysql hard nofile 8192
# End of file
There is some debate as to whether you need to reboot for this to take effect (i say debate, i rebooted, and didnt google for it as i was in a rush ymmv).
Once this is set you need to make some changes in the mysql file as well. Assuming yours lives in /etc/mysql/my.cnf - edit or add these values
open-files-limit = 2048
table_cache = 512
The table_cache should be researched (start here: http://dev.mysql.com/doc/refman/5.0/en/table-cache.html) and changes monitored. The default value is 64, so 512 should be a safe bet to begin with.