Problem loading webpages

At my apt, we have wireless. Most pages work fine and load, do everything I want, expect pages like youtube.com and others. If I go to the library, every webpage will work just how they should, all the ones that don't work at my apt. My question is what is causing this problem and how do I fix it? My roommates do not have a problem loading the webpages that I have a problem with at our apt(they both have PC's). Thanks.