Dashboard showing up blank after a period of time (no replies)

Hi guys,

I'm tracking traffic of approximately 3 million page-views/week. Archiving and deletion of older entries have been enabled, but even so, the piwik dashboard tends to become inaccessible(blank) over a period of time, forcing me to do manual purges to make it work again.
Archive.php is running every hour till completion.
I've used the CustomVariables plugin to capture user navigation data in the application, could this be contributing to the problem?

Any help would be greatly appreciated!
-Anup