Looks to me like you've run out of virtual memory. This is a Bad Thing.

I seem to remember that there's a swap partition or file lying around somewhere that gets enabled at certain times. Is synchronization one of those times? If not, maybe you could try enabling it before you start your sync and see if it solves your problem.

A little bit of looking reminds me that the swapfile is /swapfile, which, if memory serves, is actually a link to a partition. Before you start your sync, try a ``swapon /swapfile'' and see if that helps. Afterwards, you should probably ``swapoff /swapfile'' to turn it back off. (Then again, it might be turned on during sync anyway, in which case, this is all useless.)

It seems to me that if this is the problem, that it needs to be fixed. I can't come up with a good reason that it would need ridiculous amounts of memory to do this sort of operation. Maybe a transient memory leak?