problem with internet browsing.. need to repair connection everytime

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i use my laptop, which is connected to my office workgroup, by a switch. i have internet connection on one of the office desktop, on which i have enabled ICP (internet connection sharing). on my laptop, once connected to the office network, the internet connection is detected and works fine for email and chat applications. but for the web browsing on say IE, some pages/websites do not open. i do refresh, but still does not work. i then need to right click lan card connection icon, and in the support, press REPAIR. after that, the pages/websites open. this i have to keep doing every few minutes for quite a few website. i was having this same problem even with my previous laptop (i just changed to a new one yesterday, hoping will not have these problems again). the problem started i think a month back. i have not changed any hardware, etc. so don't understand what the problem is and how to solve it. please help.