My problem was Command-Shift-Option-V (Paste and Match Style) which would just give me right-pointing double angle quotation mark ('»').
Per my experience there may be at least three (3) things that might have something to do with this apparent bug (2011 Early MBP w/ SSD and did a clean Yosemite install by the way if anyone's wondering).
1) You have only one system language selected (in my case a minor language like Finnish).
2) You only have created a single user account.
3) You log in automatically.
Merely adding and setting English as a primary system language didn't solve this issue.
It seems that only after I had created a new temporary user account, logged in with that user AND/OR optioned out to log in automatically, things finally went back to normal.
The bug didn't return after I had deleted English system language and switched back to Finnish. Nor when I deleted the temporary new user account. Or when I reverted back to automatic log in.
For future reference I think it may be a wise decision to hold on to the English system language (even if you will never use it)...
BTW. In my case the previous update to Mavericks resulted in a crash (but installed after a forced shutdown). In contrast updating from Mavericks to Yosemite went all **** (and may have had something to do with a program called StartNinja which silences the start-up chime; safe to say I'll never use that one again). After this latest ordeal I no longer have any trust left that updating to a newer OS in the future will "just work".
Bollocks to that.
My IT-specialist friend copied every single file I had to an external drive, and after successfully installing Yosemite, copied them back again to my SSD (with the original intention that I could then cherry-pick just the stuff that I wanted on my clean OSX and delete the rest or just leave them there hanging until further notice).
As it turned out back home the only application that was actually still residing in my old Applications -folder was Google Music. I checked whether my apps had been hidden there - for some mysterious reason - but no such luck. If anyone has any inkling of what might have caused Yosemite to ditch my apps in to the La-La-Land, I'd be interested in hearing such theories.
For me this really does feel like Windows in the 90s all over again. Something I had thought I'd never have to re-live again... Thanks, Apple. I needed that.