Try this...
lprm -P "printer name" all
this will blitz everything in the que "printer name"
you could throw a script together which clear all ques at once if the ques arnt to busy...
I have a script called zap which clears all my ques , so when my 8 year old accidently prints that 700 page doc by mistake (and he has done this!) a quick
./zap
and all is well.
You can clear individual jobs, but this starts getting complex, identifiying the job in question. That what all thas MS bloat does!
Steve