iPrint 5.64 vs. Xerox Global Print Driver PS

A couple of weeks ago I pushed out the newest Xerox Global Print Driver-PS via iprntcmd for our Document Centre 5050 printers. All was well until the iPrint 5.64 Win7 version arrived.

As soon as 5.64 was installed, the Win7 spooler crashed on any attempt to print to the Xeroxes.

Removing and re-installing the printer at the workstation does not help.

Strangely, the Win7 desktop I tested it out with before distribution worked fine, and still works fine.
Unfortunately, that one may be the only one with Win7 SP1.

Has anyone seen like problems?
Any suggestions of what might fix it?
Maybe 5.64 should not be used until Win 7 SP1? Though it seems ok with simple HP printers.