Your only other long shot would be to rig up a temporary network or try moving your printer to a different area. By isolating the possible network issues you may be able to find out what feature on the network equipment could be interfering. This kind of network troubleshooting is not always feasible for most. The printer while in 64 bit mode may be trying to use a network protocol that is blocked or not used on the 32 bit version.
If you are interested you could conduct a test. Grab a different home router and install the Win7x64 and the printer on it. See if the problem is recreatable with a default configuration. If it is better on this network then try to isolate down what could be different between the home router and the one normally attached to the printer. You can sometimes expose similar problems by trying the printer on a different wall jack of the office.