ringtone freezing phone

[digitalpirate]

anyone has had issue when uploading self created mp4 ringtones they sound great on the phone but for osme reason when someone calls me like 20 minutes after they call i hit camera on my phone and its slow severe lag etc.. so i power down the phone turn it back on and the camera works fine untill the phone rings then it acts up again i deleted the mp4 ring tones and the phone seems to work normal any ideas?

its a nokia 6165i