I had the same problem with my 2004 Xfire (69000mi). I did something really radical: I read the owners manual which instructed me to insert a ballpoint pen in a little door located at the back/top of the shift console. It worked but I took it to the dealer who replaced the "shift assembly" (?). Cost was $520 + labor but it was covered by my very expensive primo extended warranty.

Phaedrus39