I have been trying to help a friend set up their mac book to connect to the WiFi off a new Telecom Thompson TG585v7 Wireless gateway.
We have entered the password correctly, but it just keeps saying 'Invalid Password'.
A quick google search has said that deleting the System.keychain file from the /Library/Keychains/ directory will solve it.
I have tried this, but it is still saying invalid password.
Other google solutions have been to change the Wifi channel on the router to change to a less crowded channel.
I have had limited success with this. A change of channel initially allows the mac to connect, but after a few seconds it just drops the connection again. And then when we try to manually connect with the correct password, it just says the same thing... 'invalid password'.
We have a Sony Vaio (Windows 7) laptop connecting to the same Telecom wireless gateway with an absolutely rock solid connection.
Has anyone come across this problem before?
Does anyone have any solutions?
Any help would be greatly appreciated.

Thanks