I was around 6000/12000 reputation with my guild last night. I just logged in and im 0/3000 neutral.
I went to the guild vendor to make sure it wasnt only a visual bug but i cant buy tabard or heirloom cloaks anymore
Well that sucks.
I’m honored right now, working on revered.
I had at least something similar happen with my guild rep. I was half way to honored yesterday, and had bought my friendly tabard. Some time between then and now, I somehow managed to lose so much rep that I could no longer buy a friendly tabard or heirlooms.