I encounter the same. I've just bought a license key yesterday. Before that, every few saves, ST2 asked me to buy it, which was fine with me. I've used it for maybe a week. So now I bought a license because this editor sucks if you don't have it .
Long story short: In the last 24 hours I've got three unexpected crashes (i.e. ST2 terminates) when saving using Cmd-S, after I've entered the license. Before, no crash, after, crash. System: OS X 10.7.5, ST2 version: 2.0.1 Build 2217 (stable channel). I suspect the crash happens whenever ST2 used to ask me to buy a license key.
As far as I can see, the files DO get saved right before the crash, so I don't seem to lose any work. But the interruption is veeeery disturbing and of course gives me a feeling I can't trust ST2 any more with my work, so I would still classify this as a very critical bug. But I trust the developer to take this seriously and provide a fix soon.