If it is due to the F-22 program (and not the need for bullets and bandages for the Iraqi occupation- which has also greatly affected other appropriations for the USAF and USN), it's because the USAF knows that the F-22 is the more vulnerable program for the chopping block- outrageous price tag, low production numbers, questionable cost-effectiveness and almost 15 years of being a political hot potato. My guess is that they felt the need to sure that up first since they know that it won't have too hard a time eventually getting funding for JSF through amendments to the various authorization and appropriations bills. In fact it'll be one of the rare occassions where the Navy will actually be pulling with them.
JSF is going to be the mainstay of the USAF/USN and USMC fast jet fleet- there is no credible alternative on the cards for them, it simply has to be funded. Therefore, I'd be reluctant to get too excited about this news.
(P.S. Please note that the RAF/RN requirements didn't even enter into this analysis and that's because the US couldn't give a monkeys.)