no bus code when trying to start

Need help understanding why my, up till now, perfectly running 2001 XJ 4.0 automatic with 135,00 miles won't start. Parked it in the garage for a few days to do the rear breaks and now that it's done, it won't start. First thought fuel, but even starting fluid wont get it to pop off.
While cranking it over, in the milage display, it reads "no bus". Cannot find anything about it in my Haynes manual and thought I would ask the smartest guys I've never met on here.
Anyone know what that might mean and how I might go about figuring out how to get it running again?
Thanks for any help.

Crankshaft position sensor would be a good guess. Common problem, check this post for diagnosis.

http://www.naxja.org/forum/showpost.php?p=245138530&postcount=2

Update: Ok, I just realized when I posted this that, while waiting for break parts, I had also tried to figure why my rear window defogger was not working and I checked the fuses in the passenger kick panel. While doing this I moved one from one position to the next one up (there was an open space) by accident. I added another 15 amp fuse in the #11 spot and it fired right up.
Funny that a 15amp fuse will disable the entire vehicle.
Still need to find out why the rear defogger is not working, light on dash lights up, but no heat.

Fuses don't just wear out, why did it blow?

It did not blow at all, accidentally I moved it from slot #11 to the empty slot #10 above it when I was not paying attention to where I grabbed it from. I was checking all of the fuses because I did not know which fuse controls the rear defogger. I just stuck it in the wrong spot and it kept it from starting. Gave me the "no bus" code. All other electrical systems seemed to be working, but no spark.

Gotcha. Yes, missing or blown fuses can sure cause a lot of headaches!