Problem with wireless router

Question

i have a dynamode 802.11g wireless ap router and i hvae connected it with mah laptop.it works fine as far as connectivity is concerned but i'm not able to open few sites like msn, yahoo... it works well with gmail... i can download few things but at few other places it won't download... doesn't not give nay error but just that works with some sites and doesn't work with some. i have tried everything. reconfiguration, settings and all... but no solution. can you please help.