I have similar problem. MP3 songs are fine, playing in many mp3 players fine, ID3 tags seem to be fine, v1 and v2, both. Nevo Media Player with Nevo Media Server plays them just fine. My library is large and need to browse music by folders - that Nevo Media Server does not allow, so I switched to Twonky. Right now I'm running 4.3 and NevoSL remote can browse folders with my music just fine.

BUT - when I try to play my MP3 in Nevo Media Player, it give the same error message: "The selected content is not supported by this Media Player". The only change was the server from Nevo to Twonky.

Last night I found interesting thing: when I rename MP3 to WAV - exactly the same file, still MP3, just change extension - NevoSL does not give the error anymore. There is something weird Nevo does when passing MP3. Or maybe the Nevo Player expect that Twonky does not give?

Any thoughts?