Clip 8 GB playback problem

I do have a Sansa Clip 8 GB. When I download pod casts on my laptop, they work fine. However, when I move them over to my Clip into the Pod cast file only some play back. If I reconnect the clip to the laptop and try to access and play back those non-working pod cast on my laptop, they will not work either. Any idea? 

Are the podcasts that won’t play in a format and at a bitrate the Clip can handle?  Are their ID3 tags filled in?

 Where can I see if the are ID3 taged and where can I see the bitrate?

It seems that the first 5 or 6 files do not work. All files are mp3 files. They come from the same website and web page from the same lectures/sermons. I just recently downloaded more lectures from another person site and the same thing happened.

 Well, I just went through the settings and saw ‘Formating’. So I did format my clip and put the files back on and all seems working.

Great to hear.  For the future, right clicking on a file and clicking properties should get you to the file info.