Wp super cache generate wrong folder

Hi,
By default, my website ‘www.myweb.com’ is redirected automaticly to non-www url ‘myweb.com’.
Normally, in /wp-content/cache/supercache/ there is only one folder is ‘myweb.com’. But sometimes, there appear the folder ‘www.myweb.com’ with an empty index.html file inside. So, when typing http://www.myweb.com in address bar of FF, it display a blank screen, because of the empty index.html file in the ‘www.myweb.com’ folder.
I tried delete the index.html file then everything is okie, and furthermore I changed the permission of folder ‘www.myweb.com’ to 000, but 2-3 day ago, the problem reappeared again.
Could you help a solution for my problem,

PS: I must installed BulletProof Security too, the plugin change my htacess file. Can BulletProof Security can work with Wp Super cache.

http://wordpress.org/extend/plugins/wp-super-cache/