Cannot use skype, or browse but connected

Hi,

Recently my IE and firefox would not let me browse but i was connected to the internet as i was able to use safari. My skype, limewire and MSN would also not let me connect. I have tried a system restore and Firefox then let me browse websites which did not require a password for example internet banking and facebook.

I have looked for hours to find something similar but to no avail. I have tried uninstalling norton and unchecking proxy settings etc but nothing seems to work.

Any help would be greatly appreciated