I'm having slightly different issues, but also related to loading a new paper preset.
I tried loading the one for HP Paper Backed Satin Silk through the web browser/server approach. It said that it was successfully loaded in the browser and the printer restarted, but no new preset. Stranger though, was that it changed the IP address of my printer. After a manual reset of the address, I tried again with the printer utility. Same behavior, but this time no change in the networking.
After a lengthy call to tech support, with them conferring amongst themselves many times, they said that they would need to research it more and call me back on Monday.
I'm connected through a direct ethernet connection and JetDirect, on a Mac running OS10.5.6. I have a 44" Z3100ps GP, with the latest firmware. Just for grins, I also tried it through USB and tried loading other paper presets, to no avail. I have done this many times in the past, with some glitches (like screwing up my ability to update the custom paper list), but never with a failure to load the paper presets.
Strange doings . . . so far, though, no issues with Photoshop (thankfully!).