Router randomly drops signal...

Hi, I have a problem with my Dlink 1310 Wireless Router. For a while now it has been happening but it has finally gotten to the point where I am tired of it happening.

Few things I have noticed or have done.

1) Watched modem when this happens and never shows sign of droppage in internet
2) Updated Firmware for router, and while it helped increase data transfer rates, the problem still persists
3) Usually when this happens I will click the network icon on my laptop/desktop and will see that my router has disappeared from the list of available networks entirely, then returns a few moments later.
4) Distance to router does not affect frequency of this problem

Any ideas what is going on?

How long has this been going on?
Several months

What wifi card do you have in your computer?
Desktop has NETGEAR - RangeMax Wireless-N Desktop Card. Dunno bout other two laptops but they have exact same problem. I actually bought the Netgear card for my PC thinking maybe this would fix the problem.

Have you updated the wifi card drivers?
Everything is up to date.

Do you have more than one computer in your house
Yes

If you do, is it wireless, and if it is, does it also have this problem?
They all have the same problem