I can't say that I've run into the lockup problem, but I have a full gig of memory. It COULD be that Xolox uses a bit more memory during searches, and that 1 gig is enough for me not to run out of resources, or it may be debug code that's causing the bloat you are seeing. Yea, looking at the memory usage in Xolox, I see the mem usage going up a bit, currently at 50,440k of memory used by the process, no searches going, but a bunch of things in the queue to be downloaded. Slight memory leak is my guess.

Edit: A few hours later Xolox is at 177,072k mem usage, still with no searches. I do see that there are 3 leafs connected, so I'll see if that affects it or not.