Same kind of problem here.
First.
Airport extreme looses all connected disks when the computer(s) are put to sleep.You cant connect to the disks. It will notice that the password is incorrect or that the device cant be found stuff.
Reset is needed.
After sleep you cant use the Airport tools either. You can find your airport extreme,but you cant connect to it anymore.
Connection stalls for 5-10 minutes and after that the program responds that "the device cant be found,please make sure that the ethernet connection is on and the power is on error-6722" or something.
There seems to be a lot of discussions on the apple forums,but weirdly the vanish after a while.
Apparently (?) the previous update (7.2.1) fukuced up things,and apple..surprise..tries to cover things up again.Both Tiger and leotard users are expreiencing it,so it is not just 10.5 issue.
Great.