I was very happy to see how the speed had improved on my website after the install of wp super cache. As usually I made a little check with different devices, one android phone and an iPad 2. Quite a surprise when I saw a 500 error with the iPad. Nothing in the server logs, strange. Since super cache was the last thing I installed I just deactivated the plugin and commented the rules in the htaccess.
-> in iPad my website works again. So definitively related to super cache.
Any idea ?? the most related thing I could read about a similar problem was here: http://www.litespeedtech.com/support/forum/showthread.php?t=4690