Https connections working but not http

Hi guys.

We have two branches setup as a wan through cisco routers. I will call one branch A and one branch B . Our dns server is at branch B which both branches use. Both networks are on different subnets. branch A's is recieved from the router. and branch B is recieved from a dhcp server. Everything at branch B works great with no issues. And all connections between branches have no problems. but branch A has problems connecting to web pages. sometimes a site or two will work but very slowly and the rest of the time they just time out. But if i go to the url on a secure connection it works fine. We have had someone in to look at the routers to make sure they are set up right. Both branches are with different isp's and only branch B's isp dns server are in the onsite dns server. Really we need http connections to work and not just https because the main sites we use dont have https.

Any ideas on this would be great.

Thanks in advance for any help :)