SLVR iTunes help

Hi, I just got the SLVR L7 today, and I'm trying to transfer songs from my existing iTunes to my phone. I can get the song onto my "Mobile Phone" under the Source tab, but I get an error saying that the song can't be played on my mobile phone. I don't get why I can't put an AAC song on my phone, that's why iTunes converts to. Am I doing something wrong? Thanks for any help.

is this a stock l7 or cingular l7?

check for song bit rate
i found out on my own that it wont play if songs that are greater than 192 kbps