Connection failed on my macbook pro 10.8.2

Connected but dont have connection in the internet if i search in the web? Hmmm...i bought last Feb14 my macbook pro, and sometimes i use my wifi to connect from other internet wifi hotspot, i used my iMac OS X Lion to have 3G usb internet running, then share it, so... i use my macbook pro to receive it as other mains of accessing internet, at first my macbook pro is getting connection from iMac, then it went out after a minute, i cant access internet in my macbook pro anymore, i try to diagnose but says the internet is working well, but im wondering why i can't access? Yes im using now my imac to send this message, but my macbook is down no connection even the diagnose and says "the internet is working well",

Oh yeah also notice when first use my mcbook pro to get a net connection of one of the shop we hang out, same scenario my status is connected but i cant access the web, it took me 5 or 10minutes to access the net and i dont have an idea whats going on. Hope you can give me and suggestion how to solve this.