Well in my case and many others here, the chainstay just cracked at the rear welds, luckily I noticed it before they snapped and leave me stranded. They were replaced under warranty, but I've read here that other guy just went to a dealer and got it replaced as Jamis apparently sent that dealer a few stays to spare (my assuption) check in the Jamis forum for XLT. The new one is way beefier and blingy. And for 06, they have changed both stays. Right now I just don't see where my frame could fail, only time will tell. Be sure to periodically inspect the front (bb) bearings. I have a friend who has a 03 xlt and the stay cracked just below the right side bearing, not in the weld, but in the solid aluminum part. When inspected the bearing was almost impossible to rotate, leading to the believe this caused the material to fatigue and snap! Seems that this bearing takes more gunk. And it litteraly took around 3 month's to get his stay, first it arrived and it was cracked where the right bearing goes (apparently the bore was not big enough to accomodate the bearing). And then, they kept us telling a replacement was sent, that it got lost.....well until finally it arrived. My advice just go to your dealer and ask them to replce the stay, Jamis is very well aware of the problem, so they should take care of it before it happens.
Good Luck!!