The iTunes message on the computer reads: "The iPhone "--" cannot be synced because there is not enough free space to hold all of the selected items.
I only have 321 songs using 1.97 gb of space with 2.85 gb of freespace.
When the phone isn't plugged in to the mac I get a message that says. "Storage is almost full. Go to Settings to manage this". Something like that. Can't really remember the EXACT wording of that one. Also, I just noticed that on the phone when I look at the list, all 2830 are listed followed by what looks like an iCloud symbol with a red arrow pointing down.
Hope that helps.