Well, i feel bad attaching this to the original post/thread now as the solution appears to be unrelated. For my situation:
in my model, I had one of the derived outputs as 'model parameter'. So, after the GP service ran, it populated the map contents with that new layer. I removed it as a model parameter, and now I can edit values immediately after running the GP service. The only thing I can take a guess at is that SL was getting confused with the newly added layer somehow.