I'll post this on this second thread about this same MS Word vs Yosemite problem, just in case it works for someone:
I am in the process of upgrading 19 Macs to Yosemite. I've seen this problem many times. I have fixed it in a variety of ways. Feel free to try them all.
1. Restarted, logged into Admin side, opened MS Word, worked fine, logged out, logged into User side, worked fine.
2. #1 did not work. Rebooted with Wi-Fi off, opened MS Word, worked fine, restarted normally, again worked fine.
3. #1 & #2 didn't work. Turned off Wi-Fi, plugged in Ethernet, restarted, worked fine.
3a. I noticed some people had Ethernet plugged in AND the Wi-Fi on. I turned Wi-Fi off, restarted with Ethernet only, worked.
4. A stubborn one, none of the above worked. It was a MacBook Pro. I took it home (decided to try it without the local companies spotty Wi-Fi the office has), booted it on my Time Warner Modem and Apple Airport Express, worked immediately in a normal boot.
5. Brought another to my house, #4 solution did not work this time. Rebooted in Safe Boot (Wi-Fi still ON). Started MS Word, worked fine, restarted normally, worked fine.
Seems once it is cured, it stays cured. No one has called me complaining it's crashing again. You can even put it BACK on Wi-Fi remove Ethernet and the fix holds.
It's one of the oddest problems I've seen. Not all fixes work across the board but so far one of them has worked on them, I have about 5 Macs left to go. #3 worked on the iMac I upgraded today. The Wi-Fi is often the common denominator in the mix though. Curious if these work for anyone else.