Some of my network printers pause sometimes

I have a open lab with about 76 PC’s and 4 HP Lasers, i also have the Print Manager Plus running, in order to control the amount of pages print per user.

Last week some of the printers started to pause all documents, and you have to resume the printing by hand. After doing this for all documents it’s working fine again.

Does anybody knows about this problem or how to fix it?