Any one know how to deal with "out of memory" issues when using imapsync? Is my only choice a faster server?

Here's the complete story:

In production I would like to run a backup Zimbra server in parallel with the main server in order to mirror data in semi-real time.

I know Zimbra is working on these mirroring features to complement clustering redundancy. In the mean time I have am testing the following:

I managed to setup a virtual server running Teknic on FC4 as an "open source" backup box. I also have a demo network edition of 3.0 running locally. I setup cron jobs to run imapsync to backup email messages from the network ed. to the open source ed. nightly. The sync's keep cutting out with "out of memory" errors.

I only have 128mb ram on the virtual server with the following details: I have the 128 plan

Anyone know if I can increase the amount of ram/virtual memory that imapsync can use?

I tried running imapsync from the virutal server as well as the local box -- both cut out because of these errors. The local box can use imapsync to sync with other servers fine (tried it with my previous shared hosting web co).

Any ideas on imapsync or alternative methods for backup across servers?