Print Spooler in XP

Suddenly I lost the ability to print from my Epson C80(USB) and Deskjet 820Cse(Paralell). Software said that the printers were ready and waiting, Epson showing ink levels, etc. But no printing from any app. Finally I set both printers to “print directly to the printer” and I’m printing again. But what’s wrong with spooling and how can I fix it.