Suddenly im experiencing network/connection issues for some apps

Hi. about a week ago I suddenly started to have network/connection issues with some applications:
Tweetdeck (adobe air)
Widgets that require internet (weather etc)
Safari (not Firefox)
iTunes store
Mac Software update
(these are only ones i have come across so far)

I have never had probs with these before and not sure what has changed for this problem to occur. Each app tries to connect and either hangs, timesout our causes a network error popup to occur.

I have checked the firewall and is set to accept all. It only seems to be some apps, plenty of other apps that require connection are working fine.

Anyone else having this problem and or know solution? Doing my head in!

thanks
b.

 

Netgear 54 Mpbs ADSL Wireless Modem Router DG834DSP v3 - Optus

Im bit of rookie with all this. What else do you need?
thanks

 

Ahhh that could be issue. I downloaded and tried out firefox addon foxy proxy a while ago. But I disabled it and havnt used since and pretty sure those apps i mentioned worked for short time afterwards. What can I do to sort proxy?