Sansa Clip with invisible podcast files

I have a Sansa Clip and two Sansa e200 series players. I use all for ripped music, ripped books on CD and audio books with DRM from our local library via a program called Overdrive. All work great. I've recently started grabbing podcasts from BBC, NPR and CBC, using Juice. I usually drag the mp3 podcats files to one of the players. I noticed that the Clip does not "see" these files, even though they show up in the Clip contents in My Computer. The other files I mentioned show up and play fine. I tried using Winamp to move the podcast files to the clip, successfully, but the player still doesn't show them. The weird thing is that if you look at the contents of the Clip in Winamp, the files show up and you can even play them using Winamp. The same files work fine with the other two players. I thought I'd earlier played these same podcast files with the Clip, but now I'm not sure. Ideas?