I'm running:
Gigabyte GA-8IHXP Motherboard (Intel 850E chipset)
Pentium 4 (Northwood) 2.26 GHz processor
512 MB Rambus memory
Two Maxtor ATA/133 60GB driver in a RAID0 stripe on
Promise MBFastTrak133
Windows XP with all patches in place
Xolox 1.21 (latest)

I got this error while downloading:
Version: '1.21 build 241'
Error message: 'HMODULE: 4194304 Unhandled exception EOutOfResources Exception message:The handle is invalid. Call stack: '

Also, my CPU utilization is pegged at 100% the whole time Xolox is running.