Hi. I have the same problem, even if with a different router and I managed to partially solve the trouble by tweaking the advanced wireless settings of the router.
My configuration is the following
Router: lynksys wag54g v2, firmware version 1.02.02-skidoo
PC: HP g62-b68sl with a realtek RTL8191SE 802.11b/g/n
I have read in another forum that someone was able to connect by setting the router at 802.11legacy (very old standard at 1Mbps). So I tried at first to change the WIRELESS NETWORK MODE (in the basic wireless settings) to B-only and the laptop was able to connect to the router. The drawback of that solution is that my other laptops (with windows XP) are also forced to 802.11b speed.
Next I restored the WIRELESS NETWORK MODE to Mixed and I tried to modify a setting in ADVANCED WIRELESS SETTING, called Control Tx Rate. This setting was auto, the other options are 11Mbps, 18,24,36,48,54.
By setting to any number up to 48, my Windows 7 laptop can connect to the router at that speed. This is the same speed limit for my xp laptop and my old laptop with a 802.11b adapter can also connect at 11Mbps.
I am not completely satisfied: why isn't 54Mbps speed not working with windows 7, while it works smoothly with windows xp? Moreover, I do not know if the wifi connection will go to lower speed in low signal conditions.
Another suggestion is to temporarily disable the wpa/ encryption in order to separate the wireless connection problems with the encryption ones. If you succeed in connectng without any encryption then you can solve the encryption problem:
I've read, in fact, that Windows 7 does not support WEP anymore, only WAP or WAP2.