Hi, I just installed v0.9.1.3. After that I wasn't able to get into admin area, although main site worked ok. No time to investigate so these steps seemed to work to get me back into admin:
1) delete the W3 directory in plugins via FTP.
2) delete the 4 other piles that W3 creates in the wp-content dir via FTP.
3) login to admin.
4) Plugins admin page gives warning, so I reinstalled W3, but didnt activate.
5) Delete the un-activated plugin from Plugins.
All seems ok. Only thing I've noticed is that I can't delete the w3tc dir in wp-content now. Any ideas?