Wont play on non-PC devices

Can anyone help?  I'm not a novice to MP3s, but I can't figure this out.  The tracks I downloaded from mp3fiesta plan fine in Windows Media Player, but not devices like my Zen player or from the Sync in my car.  The tracks are on the devices (they appear when I plug the USB into a PC), but are not listed on the players themselves. 

 I looked to see if there was anything wierd with the songs' tags, but they look the same as other tracks that play fine.

 Any thoughts?

IF anyone else has this same problem...

I'd like to get to the root of this problem. I'll need a MP3 sample (we'll discuss the details via email) to analyze. If anyone is interested in resolving this, shoot me an email via the contact form (or send an email to contact_@_songboom.com , but remove the '_' from the email address). I will see what I can do to help!

EDIT: It must not be a very common problem, since I've heard nothing back from anyone about this...

One idea..

What about this: Are the tracks that you cannot play encoded using "VBR" (variable bit rate)? Some older MP3 players don't know how to decode tracks using VBR, but I don't know if that is the case with your hardware.

No Playback

I as well as my children own several of the older Zen players, touch and micros. About 95% of my collection is in high quality vbr format (320 max vbr) and I have no issues whatsoever. Something else must be going on

No Playback

When MP3Fiesta tags its MP3 files (title, artist, album, etc.), it uses v2.4 rather than v2.3 for the ID3v2 tag. Some software and players can't read v2.4. You can use a ID3 tagging program such as ID3-TagIt (http://www.id3-tagit.de) to remove the v2.4 tag and replace it with a v2.3 tag.