I also own the 48 AF-1. It worked as advertised after un-boxing. Recently (after infrequent use), I became aware of the firmware update and decided to play around a bit. When I put it on my K-7, I had the same problem, i.e., it would not switch itself into P-TTL mode. I gently twisted it while on the camera, cleaned the contacts on the camera and toggled the ON/OFF switches on both flash and camera. Eventually it did communicate and now it is working fine.
I cannot say what exactly caused it to eventually communicate, but it might be worthwhile to try and reset the camera back to factory default settings, if you haven't done so yet.
Likewise, you can reset the flash, by pressing down the "Mode" button for 5 seconds.
Over the last hour or so, I have tried various combinations of settings, lenses (including manual SMC's and a Sigma10-20mm) and cannot replicate a P-TTL failure. This is with my K-7 and K-x. It is entirely possible, that your sample of the Metz 48 is simply faulty.
Edit: If it is a contact problem, it usually arises from an oxidation layer on either the camera's of flash's metal contacts. So roughing them up a bit with emery paper may help.
Last edited by Catalana; 03-02-2011 at 01:19 AM.