Internet Explorer blocked by firewall!

Hi,
I am currently at breaking point after spending 4 hours today trying to sort out my computer. My problem is that I cannot use internet explorer 7, yet I have connection to the internet as I can use my outlook mail. The error message just says windows cannot access the internet as there is a problem with the connection. When running the diagnostics on this message it says there is a problem with my firewall. I am currently on a wireless network and have a bt home hub, I called them today and they have done lots of checks and said the connectivity is fine, it is a problem my with my computers firewall. I have done everything suggested by other people on this forum who have experienced this problem and nothing has worked. I have turned off windows firewall, done a system restore, cleared all my cookies and history etc, no success. I am sooo irritated as this problem only happened today, my computer was working fine just last night, and then when I turmed it off it said 'installing updates', I think this has something to do with the problem, but my system restore didn't fix it as the only restore point I had was from today at 4.30pm! My operating system is windows xp.

Please please help me someone as my business runs from my laptop and it is a total nightmare for me!