Changed Firewall Settings

Today for the first time I changed my firewall settings. Windows XP has a built in firewall but I Installed some other firewall software on
my System to make it more Secure.I have come to know that there were many programs which were trying to access Internet. I blocked them and
that didnt make any difference.....I mean I was able to access Internet without any problem....I dont know why those programs were trying to
access Internet...One thing could be that they are trying to update some software on internet and the other thing could be that there is some
program, a trojan something which is trying to send information every few minutes on Internet....I just blocked all unwanted programs from
accessing Internet....My Internet connection worked fine for about one hour after making changes to my firewall settings....then it started
giving probs....My system was on Network but was not connecting me Internet.....and when it was connecting me to Internet it was just showing
that I got connected to Internet and was not opening any pages.....Why is this thing acting like this....Is there some body trying to block my
Internet connection....Or could there be ISP problem......I am 100% shore that there is no mistake in firewall settings....It was working very well
for one hour.....I disconnected and got connected many times in that one hour.....So I think this is not normal if its giving me problem after chaning
firewall settings....