This is exactly the problem that I'm facing! My OS is XP 64 Bit and my ML 1210 is giving the same problem (as you have mentioned - sometimes printer is forgotten and taking two attempts to print, though not always) which is really annoying and we may miss some important documents to be printed after closing them, and also the print log shows wrong number of documents printed actually (as I need to keep an eye on how many prints my users are taking)
I too used the same X64 driver from Samsung Website.
Initially I thought it is related to some physical problems such as USB Cable and I had to change as many as 3 cables for that and also tried Parallel cable as well. But glad (not to mean that way!) to know that somebody else has the same problem which now makes me believe that its driver related and nothing to do with hardware or connectivity!
Is any updated driver available for this printer (of course XP x 64) now?

Quote: Originally Posted by
xenole
Added: Found a 64Bit XP driver on the Samsung website that seems to have worked. Not overly easy to install but I can print now, although it sometimes forgets the printer is there and takes a couple of attempts.