Serpentine Belt throwing off

'98 XJ 4.0 w/AC and 165k miles
I replaced the radiator, water pump, and fan clutch about 6 months ago. It's been running great as always.
This morning when I started it, it threw the serpentine belt off. I put it back on and it seems okay, but now taking a closer look, it doesn't seem quite right.
The serpentine belt and tensioner work just fine, but the mechanical fan clutch roller looks like it sits back a little too far (recessed) so that I'm only getting about 75-80 percent belt contack. I think that may be where the belt is possibly prone to rolling off again.
Anyone seen this?

I recently had a problem where the edge of the belt was wearing and ultimately came off. I also had recently put on a new water pump. As it turns out the pulley mount on the water pump seems to be pressed on too far. I ended up cutting up another pulley and making it into a spacer that went under the original pulley. That put the pulley a bit further forward and that did the trick.

Look at the seal between the two pieces of the harmonic balancer. Is the pulley lined up straight? Is it off a bit or is the rubber sticking out??

Common symptom of a misaligned pulley. The one pictured below is shot...you can't see the other side but believe me...it's shot. It was starting to wear a hole in the timing cover and was all chewed up. It should mount flush.

Semi-recently, I had part of my belt wrap itself around the mech fan. Turned out to be too much play in the water pump bushing, pushed the belt forward. Not necessarily your case, but I would check the bolts and play in your water pump along with everything else that people have stated. New/reman water pumps can be bad.

Thanks to all for the replies.
Paradise called it. It's been running okay since I put the belt back on but you can see a noticeable wobble in the crank pully, some apparent rubber extrusion from the front, and I'm mor convinced it's the culprit as it looks to be just enough offset recessed towards the block.
This has been a gently used and well maintained vehicle by myself since purchased new off the lot in TX January '98. I've been overseas or a couple of years, homebase in Italy, and deploy quite a bit, so its one of our DD's that my wife relies on and has put about 50k miles on in Italy (LOL, tough that is). My other vehicle can fill in, though. A suby I just aquired and replaced timing belt and a bunch of other stuff.
Time to go look for a new crank pulley online (need someone that ships to an FPO) and break out the FSM for replacement procedure and that I have the right tools.
I'll let you all know how it goes. This old XJ still kicks butt and when she drove it to Croatia last year they were all wanting the 4.0!

I think I just used a steering wheel puller to get the damper/ pulley off, it was like 1 bolt then the puller not hard at all. Definitely spin ALL the pulleys when you have the belt off to make sure nothing is seizing up or has excessive play.

Note from DJ
I don’t know if you can use any of this information or not but hear it is and it FREE.

R/R Harmonic Balancer Crank Bolt
From http://www.naxja.org/forum/showthread.php?t=978307
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Tips on pulling the harmonic balancer
9-09 http://www.naxja.org/forum/showthread.php?t=1008173
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Tips on removing the harmonic balancer
Mournful Wail discovered I think it’s my harmonic balancer rubbing against timing chain cover
http://www.naxja.org/forum/showthread.php?t=1035541
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Replacing the Harmonic Balancer, how do I know when it's at the right spot on the crank?
http://www.naxja.org/forum/showthread.php?t=962575
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Tip by Joe Peters
Go for it. Rent a puller--the smaller ones you don't have to pull the radiator. If it doesn't come with an installation tool buy yourself a longer-than-stock bolt with a handful of washers. Grease up the washers on the longer bolt and use that to get the HB started on the crank, then remove the bolt, remove a couple washers, tighten it up some more, remove a couple washers, etc., repeat until the stock bolt can be used and properly torqued. Greasing the washers reduces the effort required. Beating the HB on or trying to start it with the stock bolt are not very good ideas.