w3 total cache plugin: Website breaks while APC Enabled

Hi,

I have a website developed in wordpress 3. URL is https://www.boldreports.com. I have done extensive research on caching for wordpress and have tested 3-4 plugins on this site. I have used hyer cache with db cache reloaded plugin, and the performance increase was decent. Before trying this i hve tested w3total cache as well. Botht the plugins was setup using default settings. i have not seen noticeable difference using w3tc. May be i have not done the right configuration.
After that i have studied about w3tc in detail and figured out i should use APC for caching. I have installed APC and enabled it. Kindly note that I have virtual Dedicated Server for this site and this is the only site on the server.

After enabling APC cache in apc.ini file, i have opened my website and to my surprise site was not opening in any browser. Even wp-admin pages were not opening. More strange thing is that some wp-admin pages are getting opened and some are not opening. I have disabled all caching plugins including w3tc. but the issue was still there. i have restarted the server but no solution.

Then I have disabled the APC from apc.ini file and everything starts working well.
I do not know why this has happened. I have latest version of APC (installed today) and php 5.2.14.

One more strange thin i have noticed is i can still see APC enabled (means not grayed out)in the drop-down list of w3tc caching plugin.

Can i use it here even APC is disabled from apc.ini

Kindly help me to solve this as i have to begun marketing and SEO of this site.

Thanks and Regards.
GPS