Recently a client using an open source ASP CMS system to edit a website was having with the CMS’ page timing out due to script errors. It seemed it was timing out on the MCE editor part of the page. Checking the local firewall on the machine , disabling the anti virus did not resolve the issue. I then tried to VPN to another site , which used a different default gateway ( Router ) and it worked straight away.

Upon diagnoses of the local router a ‘BT 2Wire’, it seemed the advanced filewall settings where causing the issue. As soon as we turned off Stealth Mode it fixed the issue

http://btbusiness.custhelp.com/app/answers/detail/a_id/10866/~/editing-advanced-firewall-settings