It must be coming down to money and/or guarantees. We do know that the Jets got a pretty good set of bargains in their retaining Jeff Cumberland along with Lankster and Walls. So are the Jets similarly low-balling Howard? Howard is reported to be looking for a deal similar to Phil Loadholt, which was deemed lucrative last year, but which seems reasonable given Howard's play and his position.
That said, there was a tail-off in the play at the end of the season from Howard, so are the Jets balking at a deal too big or too long? The Jets might wind up signing Howard all the same in the name of continuity, but what seemed like a very likely return for Howard is now starting to take on more uncertainty...