Ahhh...I'm also guessing that when you slid the frame/slide back together you were pushing against spring tension for the last 1/2" or so, correct?

The problem in this case is that you didn't balance on your left foot, with your head cocked at just the right angle...j/k <:

But it's sort of related: when you slide the frame onto the slide you need to make sure that the rear of the recoil spring guide doesn't move sideways enough to contact the shoulder in the frame at the rear of the dust cover, in front of the slide stop hole.

Since the bbl can rotate in the slide, and there's play between link and bbl lug, and between link and spring guide, it's not hard to get just enough misalignment to hit that shoulder. (And, just for completelness, the beveled side of the spring guide goes against the bbl lug, but I assume you knew that (:)

You'll know when you've got it right because the frame will slide right onto the slide, right up into essentially battery position w/o any resistance (other than the disconnector getting depressed by the rear of the slide, of course).

If you have a lot of trouble getting the correct alignment you might check for burrs/deformation on the rear of the spring guide, or the shoulder in the frame.

Another, less likely, possibility is that the spring guide rod adjustment is mismatched to the gun. Once you've got it correctly assembled check the screw head at the front: it should have ~.005-.015" clearance between the screw and the recoil spring cap. Any more than that and the rear of the guide will be pushed to hard against the bbl lug during reassembly, causing the bevel to ramp the rod too far away from the bbl...and into the frame shoulder.

If that is indeed the case you should be able to remove one or more of the washers under the screw head to adjust the length (use blue Loctite!).