If that doesnt work, sometimes magos has problems with putting the sequences in the wrong order. So if you save to .mdl, open it in notepad. make sure that the sequences (which are the first few lines or so) have the beginning and ending keyframes in chronological order
ergo
Sequences 5 {
Anim "Stand" {
Interval { 300, 1000 },
Anim "Walk" {
Interval { 1500, 2000 },
and so on