I'm not sure why the other message came up, but I'm sure someone else will be able to help with that. Maybe it just gave the message because the mass storage mode was off. Try turning it on and see what happens.
Posted from my CrackBerry at wapforums.crackberry.com
If you don't have it set to always enable Mass Storage Mode, when you plug in you will be given an opportunity to enable mass storage mode - click yes.