Tracking down blocks

I have several websites which i cannot access, just blank pages. The sites work when not going thru ipfire. How do i track down the culprits? i have been watching the logs time stamps but cannot peg down anything consistant. whitelisted addresses still dont work.

If the proxy is off, does the same happen?

I turned off web proxy, url filter and all the rules and reinstalled firefox, all worked fine. IE worked straight away without further intervention. reenabled proxy then url filter. rebooting each change. no problem. i only have a pinhole and a couple of other rules enabled currently. I found an old post which noted that if rules were all instead of blue/green, a similar issue was bypassed. Haven’t got that far yet.