IMac Keeps Wi-Fi but looses Internet

Question

Can anyone help with this as it's driving me crazy. my new iMac keeps loosing it's Internet connection even though it remains connected to the Modem Router and reports great signal strength with the Wi-Fi signal.
A Bit of Background Info
3 days ago I bought a new 27" iMac this is the 3.1GHz Quad-Core Intel Core i5 model and currently has 4GB of RAM which I'll be updating to 16GB in a couple fo days. This machine came pre-installed with Lion.
I bought this to replace my older iMac a 2006 model which is running Snow Leopard. I also have a MBP which is around 6 months old (I bought it just before Lion was released) and this also has Snow Leopard on it. On top of this I have an iPhone 4 and my wife has an iPhone 3G.
All of these computers and phones connect to my Wi-Fi network which uses a Belkin N300 Wireless Modem Router. This router itself is only about 3 weeks old and replaced a much older Netgear one that just failed one day.
When I was setting up the new iMac I used Migration Assistant to move accounts, documents, settings, everything from the old Snow Leopard iMac to the new Lion iMac.There were a few problems at first in doing this which may or may not be the cause of the problem I'm now experiencing. I'm going from memory here so I'm not 100% sure of the precise details but I'm pretty sure it went something like this:
1. Turned on new iMac for the first time and was prompted to add it to my Wireless Network which I did.
2. Connected a CAT5 cable between both Macs
3. Ran Migration Assistant but it failed to detect the old iMac
4. Disconnected the CAT5 cable and tried again, still failed to detect the old iMac
5. Reconnected the CAT5 but ran Migration Assitant first on the old iMac before running it on the new one. The new iMac then found the old one and the transfer began.
6. After an hour or so noticed that the transfer time was HUGE, like around 22hrs and realised that it must be trying to send it over Wi-Fi and not CAT5.
7. Aborted the migration but then both iMacs completely crashed and had to be rebooted by holding down the power button.
8. Rebooted new iMac but chose not to set-up Wi-Fi first and re-ran migration assistant with CAT5 cable attached. Transfer then worked taking around 3hrs.
9. On completion got a report saying that two programs hadn't been copied because they weren't compatible with Lion but both of these were programs I had previously uninstalled on the old iMac and this message was just referring to left over folders that hadn't been deleted.
10. Added the new iMac to my Wi-Fi network.
The Problem
The Modem Router is in the same room as the iMac (and all the other computers and phones for that matter) and is around 3 meters away from it with just a TV in between them and as such the Wi-Fi signal strength is always very strong on the new iMac (and all devices). However several times a day the new iMac just stops being able to access the Internet yet it remains connected to the Wi-Fi network. This happens whether I'm using the Internet on the new iMac at that time like surfing the web or downloading files or if I've just left the iMac on but am not using it. The cure is always the same and that is to right click on the Wi-Fi signal icon at the top of the screen, select Turn Off Wi-Fi and then turn it back on again. The length of time that I have working Interent on the new iMac can be a few minutes or a few hours it just seems pretty random.
When I do loose the Internet on the new iMac all the other computers and phones can still access the Internet and if I can still log into the router ON the new iMac and the routers status shows that it is still connected to the Internet. So the new iMac is connected to the router via Wi-Fi, the router is connected to the Internet but for some reason the new iMac just isn't getting the Internet anymore but if I turn Wi-Fi off and back on again on the new iMac it starts working again!
Things I've Tried
All the following are things I've tried without success.
1. Reboot the new iMac
2. Reboot the router
3. Turned of Wi-Fi on the new iMac, deleted my network from it's preferred network list, deleted all Airport passwords from my Keychain
I did notice the first time I did this that I had two Airport passwords listed under both Login and System (possibly caused when I first added the new iMac to the network before the successful migration?) but I deleted all of them and when I connected the iMac back to the network I now have one listed under Login and one under System
4. Added a new Network Location
5. Turned off Firewall on the router
6. Turned off Firewall on the iMac
7. I tried to use a Manual IP address but could not get this to work at all. If I used "DHCP with manual IP address” in Network > Advanced > TCP/IP settings and entered the same IP address that was automatically assigned to the iMac, 192.168.2.7, then it wouldn't even connect to the router at all. Setting it back to auto would make things work again but obviously still resulting in the dropped Internet connection.
Have I got a dud iMac, is there something I've missed, something else I can try?

Answer 1

@ Phreak777
You posted on an inactive thread.  It's been over 8 months. 
Please start a new topic about your issue so it can receive more focused attention. 
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