Websites dont open after 5 mins...messengers work ~!!!

Hi,

I have a wierd problem in my laptop( as usual). When I start my
Laptop the internet works fine for about 5 minutes. BUT after that the
messengers(Yahoo GTalk Skype etc) continue to work without any problem
BUT the Websites dont open at all. If I restart then it works for 5
mins again and stops again.
I am not really into commputers and all. So i tried whatever i cud
to figure out the problem but cudnt solve it. I read in some forum that
it might be because of CISCO VPN Client. Because i am getting this
problem only since 3 days back,...when i was trying to install CISCO
VPN Client. It showed some error while installing so I stopped it and
uninstalled it. Tried to install many times but it dint work. Since
then I am having this problem.
Please tell me what to do ASAP.

Regards
Sandeep