What version of the QuadTone RIP are using with QTR Print Tool?
I recommend starting fresh by shutting down both the computer and printer, after deleting any print jobs that may be still in the que. After turning the printer and computer back on, load a sheet of film on the auto sheet feeder of your 4800 printer, and print a test image thru QTR by selecting the Meth 1 curve, auto sheet feeder paper feed, 2880dpi, and either bi or uni-directional speed.
If you continue having issues, I recommend uninstalling the Epson 4800 print driver, as well as QuadTone RIP, then downloading a fresh copy of the Epson driver, and reinstall QTR.
Please keep me posted, and let e know if you have further questions or if there's anything else I can help you with.
Best regards~ Dana