Some users being able to read others PM's

Got a strange one you guys.

I've just integrated phpbbforum into my site. It has been running the old phpbb module for sometime but I have moved to this module for the embedded option it provides. I un-installed the old module (didnt touch the db) and installed the new one and everything seems to work fine except......... I've had reports from some users when they click a topic link they get directed to another members PM's. I've tried to replicate this issue with no luck and have also upgraded to the latest release hoping that would fix it but it hasnt. I am trying to get my users to replicate it best as they can but they are not software people so its an uphill battle.

Any thoughts would be appreciated. I will post back here if i find out what is going on with my users help.

On a side note, as soon as I installed this module, my dedicated server which just runs the site hit a server load of 4.5 and 5 sometimes. The combined includes of phpbb and drupal was just to much for it. This is a 1U rack mounted twin 2.4ghz with 4 gigs of ram running linux. I had to use e-accelerator to cache the php files which took the load down to 0.5.