Photoshop :: Image Is Not Printing Full Width

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..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).
 
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)..I tried Adobe's Chat support and got nowhere and the hold time for phone support is over 2 hours..