Often when a setting becomes "greyed" out it is because OS X has installed the CUPS driver for the printer. Whenever OS X sees a new printer it will by default load a driver for it, unfortunately sometimes with Epsons professional machines it isn't the one you want.
Things to try. In the printer preference pane, try to reinstall the printer. You may or may not have to delete the previous printer (note if you do the OS may quickly "reinstall" the wrong driver again.
You may have to do a compete clean out of your printing system which involves uninstalling all Epson drivers, then reinstall your printer driver. (Here's my write up on how to do this).
I see this thread has developed overnight, and I'm now a little uncertain what to conclude re my issue.
However, I've set about trying to follow Wayne's method as per his blog post.
Not going too well, though, as I'm not able to perform the Uninstall from the new Driver installer - the option simply doesn't arise, and so it's just installed itself again. However, in the Print & Scan System Pref, under Options & Supplies, it clearly shows I've got the latest Epson Driver (v.8.64) installed in there. So I'm thinking maybe the issue is not that I'm using a CUPS driver after all. So it's something else...
I'd do the full de-crufting thing Wayne recommends if I could find the "Uninstall" option in the Epson installer, so if anyone can suggest what I'm missing here I'd be much obliged!
As to the Common Updater, I didn't install that, but will do so now. Just to note: there seems to be a disparity of versions of this between the UK and USA Epson sites. UK site has "Mac OS X Common Updater {v.5.0:} 28-Dec-2010, 35.0MBs", while USA site has "Common Updater v7.0 posted on 05/13/10 13.6MB"
I'll install the UK one for now, but I don't expect it to fix my immediate problem
Any further suggestions welcome
Thanks again
Jim