I would run fsck and safe mode first. Here's how to do that:
1) Restart, as soon as you hear the startup chime hold the Command S keys. You'll get a Unix text screen. When the prompt come up type:
make sure there is a space between k and -. Then hit the return key. When the diagnostics say the computer seems to be ok type:
then hit return and you'll start up back to normal and see how that works.
2) Start up in Safe Mode by restarting and as soon as you hear the startup chime, hold the shift key. Keep holding the shift key until you see the Gray Apple and spinning gear. Then let go of the shift key. It may take up to a half hour to start up because the system runs diagnostics and may be repairing. After the computer starts up, then restart normally.
At this point you can try printing again. If printing still doesn't work good, I would download the Mac OS 10.5.6 Combo Update. The Combo Update is a huge download but has all of the possible contents of the system upgrade. You can get it here:
Then see how printing does.
If that doesn't work I would delete all of the printers and reset the printing system by going to System Preferences/Printing and control clicking in the white space below your listed printers. The reset printers contexual menu will pop up and you click it. Then add your printers again.