ISA 2006 : can not change password using FBA (password must meet complexity requirements)

Situation : ISA 2006, using FBA with AD authentication (publishing exchange or MOSS or...)

problem : when you log on using the "i want to change my password after logging on" this won't work and you recieve the "password must meet complexity requirement" error message.

Solution : this is probably due to the default domain group policy still being in place. and you are trying to change your password twice on one day (probably because you just configured isa and are testing this feature :-)
open up your GPMC and check the minimum password age setting in your default domain policy. if it is set to 1 day you are experencing the same issue as i have above.
it is possible their may be other causes for this problem but changing this solved my customers problem (thx 2 JPM !)