This looks like more than one problem. Lets break them apart:
Printer:
So, does it print fine in other programs? Does it print in any program? If not, try removing the Epson Class USB Extensions from the Extensions folder. The Apple USB extensions cover much of that functionality.
If that fails, deinstall the Epson drivers and reinstall, remembering to toss those Epson Class USB extensions.
As for the TIFF file problem, it sounds like the file is getting corrupted (careful, genius at work here). Now we have to get at what is causing that corruption.
The printer problem and the file corruption may be related if you are running both USB devices through a hub, and you have to be doing something like that because the keyboard takes up one USB plug and only one other plug is left open.
If either of the troublesome devices is plugged into the keyboard (which is actually an unpowered hub itself), that could be where the problem lies.
In that case, the solution is either a good hub (I prefer Asante) or using only one of the printer or the scanner at a time.
Hope this helps.
I'll continue to monitor this thread til we get you some satisfaction.