Would I have to do that manually? Also, that would just take affect on that spawned process, right? Not a permanent change.
Right. It would only change the priority of the currently running process. If it spawns a bunch of processes that run for a while and quit, you can set the priority of the parent. New processes spawned from the parent will be inherit the parent's setting. It's still temporary in the sense that the next time that process starts up fresh it will be at the default priority. BTW, just to clarify since I said to "nice" the process... you use the "renice" command to change the priority of already running processes (there's two tools related to nice values, "nice" and "renice" -- nice spawns a program with a modified priority and renice changes the priority of a running program).
The fact that your system froze could point to any number of things (including hardware problems). Have you tried looking through syslog (and /var/log/messages on debian/ubuntu) to see if anything blew up?
BTW, here's a good article on load average calculation: http://www.teamquest.com/resources/gunt ... /index.htm
Short story is that the load average is a fancy time-dependent estimate of the number of running and runnable jobs (Linux also adds in processes blocked in uninterruptible sleep, so heavy I/O can make your load average go sky high). The three numbers you see are 1 minute, 5 minute and 15 minute averages.