In above models of HP Laserjet printers, a problem of curser like vertical unwanted line which do not appear in display but prints on paper at various spots randomly. Please suggest the solution. I many of the times reinstalled the driver. The test page prints correctly.

From what application are you printing when that cursor line shows?

In any word processing software like Word, Pagemaker etc.

Have you run the maintenance on the priter? Try Aligning the print heads and cleaning the cartridges. Run the clean a couple of times. (be aware that this uses quite a lot of ink when doing so) The facillty for doing these things should be in the set or properties of the printer.

Seems like a driver problem to me.

Do you have the correct driver installed?
That matches both the printer and the Operating System?