Did you try some USB WiFi device for this laptop? As to the advanced changes, I never found that to be a cure. I continue to set the card drivers back to stock values and when that fails I use something like a AWUS036H (see google)
I live in a building with a provided WiFi connection. The password I've got is good since I was able to connect to the network a month ago. Since then, when I try to connect with my laptop (and with any other laptop), the connection fails. Sometimes it just says it failed, sometimes it seems to be connected but with no internet available, for a few seconds, then disconnects.
These are some other things:
- The signal strength is maximum
- My play station and phone connect without problem
- I have access to my router settings since the admin gave me the password to the DLink DIR-615.
- I thus know the channels used, the encryption, the bands and everything. Matched it with my wireless card... And nada!
- Rarely, when I'm patient enough and randomly changes some configuration on my card, it connects... But then fails the day after, until I successfully changes (randomly again) some advanced parameters of my card. I tried to find a pattern, but no succes during this painful month.
If anyone can help, it would be absolutely awesome.
Big love.

Chowhound
Comic Vine
GameFAQs
GameSpot
Giant Bomb
TechRepublic