Any luck with this? I am having the exact same problem with a Panasonic DP-1820E. Trying to get printing working from an iMac with OS X 10.6. Same symptoms you describe. I can install the printer with the proper PPD file from Panasonic, but when I try to print, the print goes to the queue and pauses the printer. If I try to resume the printer, it pauses immediately again. Once I delete the print job and resume the printer, it resumes fine and is at Idle status.
The Panasonic manual for installing the driver only mentions up to OS X 10.4 or 10.5 depending on which manual, and they both refer to using Appletalk as the compatible protocol. Well, unfortunately OS X 10.6 has done away with Appletalk, so I think I might be out of luck. The manual does say "Selecting LPR connection is available, however the operation is not guaranteed".
If there is anyone out there who has gotten this working with LPR/LPD, please let me know. Thanks.