Randomly can't ping or visit google addresses

[IronComet]

Good Afternoon,
I have a firewall in place with the latest version of PFsense.
It is set up to manager a captive portal and has a opt1 interface servicing several access points for WIFI.
A couple weeks ago after working fine it will randomly stop allowing users, both hard wired and wireless, from accessing google.

I have found that you can not ping any of the google ip addresses either.
I have backed up the config and set the firewall to factory defaults and reapplied the config and I have also moved the backup to a second new firewall.  So it does not seem to be hardware related.

If you take the firewall down and hook directly to the modem it will work fine.  I also found that if you disabled the opt1 interface and then reboot it will work for a bit and then go down again and then after a period of time it will come back up.

Is there anything i can do to set a log or something to find out what is causing this issue or does anyone have any troubleshooting tips?

Thanks!

[TheSypHunterGeneral]

Are you running any IDS, etc. i have SNORT running and noticed a few months ago that google ip addresses would somehow get on the block list, don't know whats google has changed? i ended up creating a Google white list and placed all google wildcard domains on it, you can google how to do it. there are heaps