Well Blackcat2000 and Jimangle, you both have a situation that sounds very familiar, my 2000 XKR exhibited the exact symptoms as your yours some time ago. Matter of fact, it happened just after a plug change. First, lots of white smoke, then hydrolock!
After some prelim assesment, I found the 3rd cyl, right bank, had crompromised head gasket. No water in oil, just a slight break in gasket between water jacket and cylinder. I had only owned my car for a short period of time, and although beautiful and well maintained, I suspect that may have been the reason the previous owner let it go. I am finding this can be an issue on 4.0 supercharged engines.

Upon replacement, the 4.2 head gasket is the way to go. Had always smelled coolant from day one, but it took awhile for this problem to finally rear its ugly head. Signs of a "stop leak" product were evident upon closer inspection.

After accepting this as a fact, I put my cat in the garage and embarked on other "projects" as needed. Final decision was to wait until this winter, disassemble the top end myself, and after some serious research, send my bits off to Stiegemeier Porting Services, since all will be down and apart, send the heads, supercharger, and related bits off for a valve job and porting and polishing, these guys are Guru's for Ford supercharged engines, and have experience with supercharged Jags to boot. What the hell, its all apart anyway!! As an old drag racer I see these performance gains as efficient and safe with out worrys of increased cyl pressure or heat by increasing blower boost. Good luck to you both.

Best to ya,
BK