2 gb ram free, ubuntu natty.  The vm itself is 32-bit, running on a 64-bit ubuntu lucid host with VirtualBox.

Doesn't happen every time, probably one time in three though.

Now I just try to start bitcoind, update the blockchain, do my transactions, and get out.  But if I forget and leave it running, often the entire instance will lock up.

To build a business on this, I'd like to know that I can leave it running 24x7 with no issues.