LG LD550 TV Doesn't Maintain Wireless Connection To Internet

I recently purchased an LG 42" LD550 Flat Screen TV. This TV is supposed to wirelessly connect to the Internet in order to stream Netflix, YouTube, Vudu, etc. I've purchased and connected the required LG AN-WF100 USB Adapter (dongle). My desktop computer is a Dell Studio XPS 435T/9000. My router is a D-LINK WBR-1310.

The TV simply won't maintain a connection with my network. Sometimes it will find the network just fine for several days -- then it disappears (in the list of networks, only my neighbors' networks show up, not mine).

I follow the steps in the LG manual: I go to "Network" and select "Wireless"

It then shows the AP List. My AP (SSID) is almost NEVER listed, but when it occasionally is, I select it and type in my Security Key. It then proceeds to scan, and 95 percent of the time, it comes back with the error message, "Connection is Failed. Going Back to the List". The other 5 percent of the time, it ACTUALLY CONNECTS for a while (sometimes a few minutes, sometimes a few days). Then it disappears, and the whole cycle starts again

It's been a week now since I actually got connected! Is it the TV or the router? My router works with other devices (laptop, Nook eReader, second desktop computer), so it HAS to be set up right, doesn't it? The entire reason for buying the TV was so that I could wirelessly stream from the internet, and I feel cheated.