I contacted the Archos help desk folks who were very responsive and figured out that those podcasts were produced at a low sampling rate and for some reason this little Archos player couldn’t play them. The Archos folks promised to put it on their list of fixes. Oddly, all those podcasts play just fine on my older Archos AV 500 media player.
In the meantime I found a fix. Open the mp3 file in Audacity, change the sampling rate to 22,050 khz or 44,100 khz (“Project Rate” menu at the bottom of the work screen) and Export as MP3. The file is bigger, but it plays on my player.Â Yay.
And if anyone is confused by bit rates vs sampling rates, this post Bit Rate Resolution and Sampling Rate for Dummies has a nice explanation that made sense for my non-audiophile brain.