Unfortunatly the PXA255 is rare... Well, rarer than the PXA250.
I'd make a NAND backup for you, but for the fact that I've got the PXA250... Sorry. :/
Also remember, when making a NAND backup, the ENTIRE Zaurus data is copied... PIM data, apps, settings, etc.
I'd suggest once getting a NAND restore working, just re-flash and re-format it right away, though.