Dragging Files from iTunes

Some of my files are FLAC files.  I normally convert them to WAV files, then load them onto iTunes and further convert them to AAC files.  When I try to drag these files from iTunes to Sansa Clip, it will not allow me to drop them into the music folder.  Not sure what I’m doing wrong here and would appreciate any help.  Is this an iTunes problem?  If so, perhaps I should convert via some other program?

The Clip does not play aac files; that could be the issue.  Mp3, wav, wma, flac, ogg, Audible. 

Also I have found that you need to be in MSC mode for itunes drag and drop to work directly to the player.

Thanks for the help.  I wasn’t aware that I could adjust iTunes so that it would decode into MP3 instead of the default AAC.  I’ve now made the default MP3 on iTunes and everything is working fine.  This Sansa Clip is a great little gadget!