If this is still a problem for you than here is what you can do
Open up airport utility, you will be able to find it in the utilities folder which is inside of the applications folder. Click on the time capsule, then click on the edit button that is on the bottom of the popup. There you can change your base station password. This will not change you wireless password.
This may work if you have a time capsule but this is not my case. When I try to do as suggested, the system says there is no time capsule and this is correct. I am using Time Machine backing up to an external drive.
A full description of my problem is given here:
Any help you can give me will be much appreciated.