I've got a new iPhone for only a few months, and I have no problem making custom ringtones, but sometimes, when i sync them to my iPhone, here comes the problem: "it shows up as a ringtone in iTunes, but it won't sync to the phone. I've restarted my phone several times, hoping that would do it. I've removed all my ringtones, then re-synced them...but still nothing."
I searched the forum, Googled this and found that a lot of user have the similar problems but no sound solutions. It took me a long time to finally get this problem fixed before I found an article how to sync iPhone ringtone on mac. I learned that iPhone Ringtones have a lot of limitations like it's up to 30 secs, none of the song fields (song name, artist, composer, etc) have special characters etc, which I didn't know before.
Well, if you have the similar problems, I am sure that can help you out.