chiduke i think because this problem exists in every browser, its not an issue with Firefox browser, i think your windows machine is under attack by some malicious software or your spyware is blocking the access to internet. Did you say you are able to access for some time after you reinstall Firefox, i don't actually know why it works think its working until the malicious software or your spyware detects Firefox's presence and blocks the internet. Try to start your machine in Safe mode, i mean windows. (Don't know how as i don't use windows but i know there is a safe mode when i Googled it say you can access internet only in safemode with networking option enabled so make sure you open in that), try to access the web & test for few hours if it works then its a problem with windows. May be you can ask windows support for help.