I have the same problem. The behavior is identical to what one would expect if you were to click and drag a tab - therefore I assume the issue stems from click handling, where the click is being identified as a click-drag as opposed to a plain click.
I also believe this a performance-related issue. I've got another thread
that discusses my experiences with plugin_host.exe and a pretty terrible memory leak. ST3 just seems to be "laggy." (I know, shoot me - that's a terrible bug report).
Also, I noted in the other thread that this could be related to directory traversal - I've noticed that sometimes there's a "crawl" process that seems to instantiate and disappear at startup - not sure if that's helpful.
Sublime Text 3 - build 3054
Windows 7 x64
AMD Phenom II X6 1055T
16 GB RAM
One ATI FirePro V4800 (FireGL) with 3 monitors
Aero is enabled