I'm having trouble with a couple of albums on my iPhone. When I play the, the iPhone indicates that they are playing, but it's silent...

...now, I checked the info for the albums, and both are encoded in LAME3.9 and VBR. I'm wondering, is the problem with VBR? LAMe3.9? A combination of both?

(ps: I tried searching, but try searching with keywords lame (most threads have it) mp3 and vbr (the latter two are ignored!).