I converted all of my mech ranks into Forging (424), chose a career in armorsmithing, and picked up several techniques. I then proceeded to craft one "challenging" item, and my Forging locked before I even finished it. I was getting very small pulses when it absorbed (about half of one percent) though. I then logged out and back in, and it was automagically at 6/34 instead of locked, and my pulse sizes increased back to normal. I think the conversion didn't update the size of my experience pool in accordance with the number of ranks, so I was working with a zero-rank-sized pool at 424 ranks until I fixed it by relogging.

Thanks,
-Life Sustainer Karthor