The hood latch system in the XJ consists of two latches and strikers, tied together through a bellcrank assembly riveted to the middle of the hood. This, in turn, is attached to the cable assembly that snakes it's way through the firewall to the kickpanel.
I would bet that the cable is corroded, and hence sticky. It MAY be possible to remove the cable assy from the vehicle, and using liberal amounts of oil, PB blaster, etc., work the cable back and forth in it's sheath until is slides easily. Then, lube the bellcrank, and reinstall.
If that fails, your best bet is a NEW cable assy from the dealer. I would bet most cables in XJ's in the boneyards around Albany, NY, will be as rusty as yours. That wintertime salt vapor from the road plays hell on the underhood stuff.....