Printer driver Network printing?Port chk

Hi

My first problem is a HP 4L LaserJet. It printed ok and started to print an extra page with the letter @ on it, after the original document finished printing. Then it started printing Garbage. I removed the printer and reinstalled it as well as the four network connections to it thorough the computer it is connected to. It worked fine, but the next day all started over again same story. Some other IT company was called out and the same was done as above except the Reinstalling of the network connections.
It worked fine for a wile but the same problem is starting again but not always.
Is there any advice out there?
We use windows 98.

How can I test If a printer port is blown or not?

Thanks
Melt