Upcoming Xbox 360 update locking out 'unauthorized' Memory Units

With next week's XBox360 update a block for 'unauthorized' memory units is included. Major Nelson wrote this on his blog:

"When Preview Program members start receiving the Xbox 360 system update next week, one of the changes is that unauthorized Memory Units will no longer work with the Xbox 360. If you have moved your profile or saved games onto one, you had better move it back onto an authorized Xbox 360 storage device prior to taking the update. If you continue to use an unauthorized Memory Unit after the update, you will not be able to access your stored profile or saved games."