Could having multiple displays cause WoW to crash once you click start in HB ? This is in regards to Windows 7. I know this sounds like a silly question, but I'm curious.
Not unless you have a bridge with an off site accelerator; and even then its rare. Go into your Honorbuddy folder -> Settings and delete GlobalSettings.xml Start HB again. If the problem persists, go to your WoW folder -> Logs > gx.log and give us the error.
unless you're using some sort of special gpu-loadbalancing driver (like external graphics booster like alienware supplys and/or usb-gpus) i've never seen this happen. afaik honorbuddy does not read from your gpu ram. most crash issues in regards to this are a result of a faulty system ram configuration (broken modules, bad blocks and so on)
I used to use 2 displays with HB and never had any display related crashes. Worst thing to happen would be HB would continously try to open offscreen (especially the menu where you choose CR) so I'd have to try and work around that.