@morrow without logs this will be hard to track down. can you ask your administrator to open up a support case for this?
On the 5th of February, from 14:00-14:25, Steve Hardy (CTO at Zarafa) will give a speech in the MySQL devroom at Fosdem. During Steve will discuss how you can boost your MySQL innodb performance by implementing a prefetch mechanism.
Follow this hyperlink for more information: http://forge.mysql.com/wiki/FOSDEM_2011_Developer_Room