Why dies my wireless modem forget it's password?

Every once in a while my wireless modem stops accepting the password until I shut off the power and turn it back on. What might bs going on?

Its probably not the password but something else, it froze up or something. See if it has the latest firmware and it is setup correctly. If you can, check to see if you can flash dd-wrt on it.

I agree. Make sure to get the latest firmware. Many routers are initially shipped with firmware that just barely works and have bugs in order to meet the deadlines. They believe it is ok as the user can get the updates later on. Unfortunately, many customers never update the firmware to the latest version.