So it's a security issue rather than a mac filtering issue.
the security type that you were using, as it a default password? or had you used one of your own? (sometimes certain routers will let you enter to many letters into the security phrase/word and it will only use the ones it needs but new devices might be more picky about the length)
does the Asus definatly use the type of security that the router uses? (a common issue with ipod touches!)
try changing security type until you get one that all your devices are happy with.
(There are loads of other things you can do/try and I'm sure someone will be along in a minute to pick up on stuff I've not mentioned, but the changing security settings until it works approach will be easiest if your not 100% sure of what your doing, just make sure you take it 1 step at a time and don;t foget what you did incase you need to undo it again)