somtimes

What do i do when im in a server and it says warning connection problem but my connection is fine?

OK i have the programe milkshape 3D 1.6.6a i made a tail for my ssj4 gotenks but when want to export the file it gives me a warning: Found vertex with invalid bone assignment! Model not exported! what do i have to do??? Here's a pic a made (the gotenks ssj4 reskin) if u can't see...