The system log might have a better error. It's possible that you don't have perl installed, or it's not on properly.
If a reboot doesn't fix it (probably won't), you might try to uninstall lightsquid, squidguard (if you have it), and squid, and then reinstall them in the reverse order: squid first, then squidguard (if you use it), and finally lightsquid.