Same problem as well. Im certain there was a sticky at one point about the problem, which is now taken down for some reason.
Though its a "small" bug, its freaking annoying, as it halts everything just as much as it would have if you had been stuck underground. No quests can be completed, taken or otherwise. Logging in and out dont help at all. Some times after maintanence it seems to free up a few if you are lucky. Never all of them though.
I find the whole pending rewards stuff kinda weird. Why on earth have they put a cap on the maximum you can have at a time, and even so, why make you unable to interact with ANYTHING at all when youve reached it? Makes little sense indeed..
Fix it.. Customer Support is a total joke at the moment, with standard replies for everyone. We dont contact Customer Support for something we already know. We know its a bug, we just want it fixed. Preferably before you leave us to wait for an unspecified timeline, being able to do pretty much nothing other than roll on to another character. Which once again makes us prone to get the exact same bug sooner or later. Rinse repeat. It's quite a vicious cycle, id say.