I have had this feeling several times. I think what's helped me a lot is that I play several instruments, (I'm guilty of feeding the guitar thread). If I feel I've reached a stagnant point on keys, I just focus more on guitar for a while and learn a couple new licks and tricks. When that gets old, I work out my sax technique. I never totally abandon 1 instrument for another though, at least not my main 3. If I do, I'll go backward, but I do redirect my focus for a bit.

Another thing that has helped me immensely is the fact that I've been hired to produce/arrange/perform, on 2 different CDs in the past year. One is more rock/softrock, and the other is quite folk/country. I am responsible, at least in part, for making these artists sound good; to make their songs interesting to listen to, to make them appealing/marketable without becoming stale. Combined with my own more jazz oriented efforts, I've had more than enough stimuli to keep my brain and hands learning/creating. I listened to a whole lot of music I wouldn't have otherwise listened to, and I expanded my horizons that much further.

Finally, playing live gigs helps as well. You can easily get bored playing for yourself all the time, but sharing your stuff with people who have never heard you before, or with people who don't listen to you every day, just makes you feel fresh. Your music doesn't seem as boring, and your playing as stagnant, when you've got people listening and enjoying what you do.

I don't know if that heps at all, but I might suggest starting on another instrument, learning to play different styles of music, work with other people, (more people=more ideas), and try to play live.
This formula won't work for everyone however, as in Doug's case. He seems to have played out a lot, and with many people, and is growing tired of that. (at least that's what I gathered from his post.) So there's no 1 way to get over this hump. Just know that you'll get over it though. I always have, but I feel myself sliding into yet another. I hate it when that happens. So do you know what I've done? I've ordered some ethnic music. Maybe i need to get into African/mideast sounds for a while. I just keep plugging away, always expanding.