Shows good internet connection, but can not access.

A few weeks ago my computer would connect to wifi or a cable like normal, telling me its connected, however mozilla and ie would not be able to access the internet (along with all other programs). This has happened at home, library and work, so its the computer. At first i did a system restore and that fixed the problem, but it came back after I restarted the computer I believe. Hoping for any help out there, getting desperate.