Miker:
I too have one of these Craftsman torque wrenches and the exact same thing happened on mine. There is actually a nut that hold it all together, but you have to pry off the plastic cap at the end of the handle to get to it.
I took mine into the local Sears, and they weren't very cool about it. They said that they wouldn't warranty it and that I would have to pay them to have it re-calibrated.

This torque wrench, although it was probably 4-5 years old, had only been used maybe 4 times-max! The folks in the small town Durango sears were kind of jerks anyway, so I may try taking it to a different store in a larger town and see if I get a different response.
Hope your luck is better than mine...
Btw, my Dad had a Snap-on torque wrench, was used all the time, and it never came apart. And the handle was metal.

He bought it used so he didn't have to pay the premium price it would have otherwise gone for. Great tool at a good price.