LG enV tranfer problems

I got a new enV and i want to put music on it a have formated the card and everything and im trying to drag and drop music to the my music folder on the sd card but it said not able because the card cannot be modified. I know it will work earlier today i got it to but something must have happened because i can get anything on there agin. I have a mac in case you need to know any help would be appreciated.

Is the card write protected?

From what I have been hearing....mac's and SD cards don't mess well with each other.