I have the same printer as you and did had the same 99% complete printing problem several months ago.
Unfortunately I can't remember how it was fixed!
But have you tried the following:
1. Uninstall & then reinstall the printer.
2. System restore back to when it worked.
3. Clean install XP.
I believe one of the above fixed my problem and the printer has been working great ever since.
Before anyone says it...I KNOW there's a forum for peripherals
No one answers the questions there though
I have a Lexmark X1150 all in one printer...the rest of it works fine but when printing it will print the page(and finish) but SAY 99% complete then stop
Nothing I've tried so far can get it to acknowledge the printing job is done
I might have other printing jobs "pending" but until it KNOWS the first job is truly done it won't go to the next one
If I reboot it will then go to the next job but the same thing happens when that one gets to 99%
It can even be a more than one page job and it will do all the pages and still stop when it says 99% complete
What the heck is going on?
BTW I DO have Win XP so don't chew me out too much for posting here
PS I'm not the only one with pretty much this same problem...over in the peripheral forum there are at least two others who describe much the same thing..we all have different printers too