I have just fixed the Epson "toner waste bin full" warning in the Print Queue windows this morning!.

Firstly I thought I'd check the printer drivers on the Xserve through which the clients print via IP. I opened print set up and the Options Supplies/driver and selected "Select Printer Software" where it showed duplicate drivers for the affected printers. I looked in the Printers/PPDs/Contents/Resources and found the driver existed for the Epson C9100/C9200 in the en.lproj and the top level of the Resources folder. I deleted the drivers from the Resource folder top level and then forced all the Epson printers to select the driver from the en.lproj folder(as I assumed from previous occasions this is always the correct file path for PS drivers) using "Other" drop down menu in the Driver window in Options supplies/driver. As soon as I printed the "warnings" cleared on all the printers queue windows. Why the PS drivers existed in "duplicate" I don't know but its certainly cleared the problem now. Whilst this error warning situation didn't affect printing output etc it was good to be able to solve the issue!