Ive been troubleshooting since i got the phone 2 days ago and heres what i came up with...
-connect via USB to computer as mass storage
-then view files on computer
-then create a folder called "alarms"
-drag any mp3 file (maybe also .wav) into this folder.
whatever files you place in "alarms" folder will work on both setting custom tones for text messages etc, and alarm clock notifications in the built in tones list.
Also, you can create a "ringtones" folder in the same way as you created the "alarms" folder. once this is done, whatever files are in that folder will show up in the built in android ringtones list when setting a ringtone.
im guessing whatever files in my "alarms" folder will also work in the calender as well.