A wireless signal can be dropped for a myriad of reasons.. just takes some troubleshooting.
Try turning off the router for about 5 minutes to allow it to reset then tuen it back on.
As soon as I move the laptop in the room where the router is it becomes as before - fast and no problems
Check out this support article > AirPort and Bluetooth: Potential sources of wireless interference
And try deleting the network preferences file. Could be corrupted.
Open the Finder.
From the Finder menu bar click Go > To Go Folder
Type this exactly as you see it here;
Move the NetworkInterfaces.plist file from the SystemConfiguration folder to the Trash.
See if that made a difference. Try your Wi-Fi.
Also, you may have interference from other wireless networks, get on your router and change the chanel. Turning the router and modem off periodically can also help as suggested. All binary circuits need to be reinitilized periodically. If you have a wireless phone it can also interfer if the band is similar to G (2.4 GHz). Your router is not an G/N so the N band is not interfering, but that can happen when you have a dual band router.
Thank you very much for your quick responce. I have moved the network preferences file to the trash but still no succes. I have already restarted the router and the modem many times with the hope to rectify the issue. Note that the ipad, ipod and iphone use the same wireless connection anywhere in the house with no problems. So it could not be other wireless network interference. I think that could it be something in the MBP wireless network settings. Something in the TCP/IP or DNS etc. settins may be!!!
Just in case you want to check the channels nearby wireless stations are using, you can open About this Mac from the apple menu, choose More Info ..., and then select Wi-Fi under network. It should list all the visible stations and channels the channels they use. There must be a myriad of apps that will provide this information, too.
If you move the MBP into the room where the router is you are reducing the attenuation of the signal. That means either the wireless card or antenna have a problem or the wireless radio on your router does. If the other devices work, it may be the card on the MBP. In the Preferences >> Network >> Wi-Fi click on Assist me... (near the bottom) and run through the diagnostics. Do it close and far away from the router.
The mechanic of the wireless system in the MBP are a bit different than you other wireless devices, so it can also be increased interference by other routers, cordless phones, etc (on the 2.4 GHz band). These all increase attenuation. If you change the channel on the wireless radio on the router it may cut through some of the interference.