What to do when Parallels brings the System to a halt

I don't know when this started, but recently whenever I try to start Parallels (which admittedly doesn't happen very often), my whole System comes down to a halt. Well, not completely, the system is still running, but it won't even let me switch between applications in a responsive manner. Even the mouse movement isn't smooth anymore.

Note that this is with Parallels 2 on Mac OS X 10.5. The system is a first generation Mac Pro w/ two 2.66 GHz Core 2 CPUs and 3 GBytes of RAM. So the system could use a little more RAM, but apart from that it shouldn't have any issues running Parallels. And in fact, things used to work just fine.

Anyways, here's a workaround I've discovered today:

$ sudo /Library/StartupItems/Parallels/Parallels stop
$ sudo /Library/StartupItems/Parallels/Parallels start