From what I've been able to glean, the kerfuffle over the salary cap proposed last friday is a microcosm of the whole mess.

So the league initially proposes a salary cap structure, and the players propose a more generous one. Last friday, the league says essentially "okay, well... what about this number in the middle?" and what the league presented did not address how the cap might grow if the game grows beyond projections. So instead of asking "well, we might be able to work with that provided the cap increases x% of the total money the league makes beyond projections" the NFLPA presumed that the league was saying "you get none of any money above and beyond projections" and storms out in a huff to file a lawsuit.

I've honestly never seen two groups of adult men, with highly paid lawyers on staff to advise them, less capable of actually communicating with each other.