This has been discussed in other threads but here it comes again. This happend to me and after reading a few posts it doesnt happen much anymore. The error usually comes up when you still have a search window open, and this is something that I have noticed myself. Before I close xolox completely, I make sure that I do not have any of these windows open. I also read somewhere that uploading or downloading on close can also cause this error, it was suggested to try pausing the download before closing. I have also noticed that I dont get as many xolox crashes when i keep my system defragmented and in tip top shape. Happy Downloading.