I received the OTA notice and got the same as you. After reading here I tried the myriad suggestions to force it and try to install (changing the date, clearing cache, making more space, etc, etc). I can now bring up the OTA notice at will but it will not install. Seems like I need to factory reset.
I have given up. I don't think it's worth it from what I hear. My phone works as it did for the last year and a half, good battery life and lots of info I don't want to either risk losing or take the time to get back to how it is now, just to have the latest.
If there was a compelling reason to update to GB, I suppose I would.