I removed my previous version of the plugin and installed s2 2.11 with wp2.0.7. I no longer have the S2 icon in the quick-edit toolbar and inserting <!subscribe2> into a post has no effect.
I installed as directed, modified the php file for my subscription page, enabled the plugin and set the options for s2 to appear on the toolbar (as I did with previous versions).
Perhaps all the flurry of activity from2.0.6 to 2.0.7 has caused something to break.
At least my old subscriber list was not removed!