Apparent memory leak/memory allocation problem with 2011

I have this problem consistently on my W7 Pro x64 PC using 2011 (latest build). I have raised a ticket with Acronis Support but thought I'd discuss it here too.

My backups are pretty large, mostly many 10's GB, I don't know if that might be relevant. Some time after starting a backup (say about 30 mins, not quite sure). Memory utilisation on my system, with 4GB RAM suddenly leaps to about 99% used. User interaction becomes impossible. Even the mouse will freeze in position for many seconds. The disc is thrashing like crazy. When the backup operation finally completes the memory utilisation drops right back down and the system is responsive again, but this does not happen until the operation is fully complete - after any validation and consolidation - and if, for any reason, the backup needs user input, e.g. disc is full, Acronis will pause still with memory full. The system is so unresponsive it can appear as if it is hung.

If no problems occur the backup will eventually run to completion normally, the memory is released and all is OK, but the system is unusable during the backup process (after the first few minutes).

Anyone else seen this? I have not seen it on my x86 system so I suspect it is an x64 issue.