, 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".
Deleting/trashing Photoshop preferences is always the very first troubleshooting step. All you need to do is hold down Command+Option+Shift on the Mac (or Control+Alt+Shift on Windows) as you launch Photoshop and keep those keys down until you are presented with a dialog box allowing you to delete Photoshop's preferences.
But can you explain how a corrupt preference file could possibly result in the behavior I describe in my original post? What do "preferences" have to do with the bit-stream PS sends to the printer (especially since it was only happening when the file was sized to specific dimensions and the "error" in what it was sending was different every time it sent it)?
As a software engineer myself, I would never advice someone who calls with a bug report to do a "factory reset" AS THE FIRST troubleshooting technique...because it prevents you from actually troubleshooting the problem. It might get the person going again but it doesn't help FIX the problem and prevent it from happening in the future. Just sayin'
also, by removing the preferences file (i.e., copying it somewhere else and not deleting it), rather than doing the Ctrl+Alt+Shift+Launch described above, I can now go back and figure out write down all my preferences so that I can do a "paul reset".