Print output not as wide as it should be (CS5 on Epson 3800)

Question

I'm having problems printing (to an Epson 3800) on 17x25 paper (the image is 16x24 @ 240dpi).  The image is not printing the full width of that it should.  The odd thing is that it fills a different width every time I try to print it.  I have tried multiple images and the same thing happens, so I do NOT think it is something specific to the image.
I suspect it is a problem with my printer.  But after spending almost 45 minutes on the phone with Epson, they claim is must be a problem with PS (I'm using CS5 [12.0.4]  on Windows Vista 64-bit, SP 2 machine).  Epson support had me save the image as a JPG and print it from Windows native print util (and not PS), borderless on 17x25 paper and the printer was able to print the full width of the paper...they thus concluded it was not a problem with the printer...but I'm not so sure, I think it could still be a problem with their printer driver (and not a problem with the print head physically not being able to move that wide).
I've printed hundreds of prints this size with this version of CS5 on this exact same machine and printer and never had a problem bef
The "native" dimensions of the image are 2336 x 3504.  I have resized it to 3864 x 5796 (which is 16.1 x 24.15 inches @ 240dpi).  The first time I printed it (where this problem occurred), it printed about 12 inches wide; the 2nd time about 11 inches, the 3rd time about 13 inches.  Note: the image is NOT being scaled, it is printing at full size but it just being cut off.
The weird thing is that if I size it to any of the other 4 sizes I regularly print at everything is fine (5 x 7.5 on 5.67 x 8.33 paper; 8 x 12 on 8.5 x 12.5 paper, 10 x 15 on 11 x 17 paper and 12 x 18 on 13 x 19 paper).
My first suspicion was that their was a physical problem that was preventing the print head from moving that wide.  But the experiment the Epson tech had me do shows that the print head is not "blocked".  Thus, I can only think that there is either: a) CS5 is someone putting an incorrect "bounding box" in bit stream it is sending to the printer or b) there is a problem with the Epson print driver in that it is interpreting the "bounding box" of the image incorrectly (but only when sized at 3864 x 5796).what m
Does anyone have any ideas about what might be causing this or how I could fix it?  I have a customer waiting for prints (that they've already paid for!).  Let me know if there is any further information I need to supply in order to further diagnose.
p.s. I tried Adobe's Chat support and got nowhere and the hold time for phone support is over 2 hours...so I thought I'd try here

Answer 1

, Well, I finally got thru to phone support.  They told me they couldn't help me because I hadn't updated to CS6.  If I wanted them to help me I would have to pay them :-(  I asked to speak to a supervisor because has never been the their policy before (I got phone support on CS3 as recently as 6 months ago without being asked to pay for it).  After yelling at the supervisor, he agreed to transfer me back to the 1st-level support person and instructed him to try some simple diagnosis and if that didn't solve my problem then I would have to pay for more support.
The 1st-level support told me to:
1) quit PS
2) remove the Adobe Photoshop X64 CS5 Prefs.psp file from C:\Users\[my username]\AppData\Roaming\Adobe\Adobe Photoshop CS5\Adobe Photoshop CS5 Settings (path may be different depending on your version of windows)
3) restart PS
4) open/resize and print my image
low and behold, that solved my problem!  I'm happy!  And I didn't have to pay for it!
I still don't know exactly what the problem was, but somehow a corrupted preferences file was at fault.
Now, all I have to do is get my preferences set back to they way I had them before the "factory reset".