My .htacces file was getting updated and causing 500 Internal Server error, even without changing any W3 Total Cache settings. I was originally using page caching enchanced (disk enhanced), but changed it to disk basic as I read it would no longer use the .htaccess. However, I am still getting the same issue, though not as frequent. I suspect when it is updating .htaccess for browser caching.
-a shared hosting account
-w3 total cache 0.9.2.4
-page caching enabled (disk basic)
-browser caching enabled
-miscellaneous settings left to defaults (checked: verify rewrite rules, enable news dashboard widget, Enable Google Page Speed dashboard widget without an Page Speed API Key.)
I have not used other caching plugins before.
I read on a forum that someone that had done an automatic upgrade experienced a problem like this. I had originally install w3tc 0.9.2.3 and auto upgraded to 0.9.2.4, but then deactivated and removed plugin completely and reinstalled 0.9.2.4. Still getting the same issue.