If you are in Windows, can you check the Windows Event Viewer/Application section to see if you are hitting an appcrash?
Look for an EventID 1001 item, it's an APPCRASH in Studio One, sub section ---> "mp3handler.dll"
I'm hitting the same thing and was just going to file a bug.
Workaround: I was able to "re-encode" the MP3's to get them working using MediaMonkey. Although any MP3 encoder might work for you.
EDIT- Further examination using MP3Diags - Discard invalid ID3V2 data -- After doing this to the file, it worked.
Fault bucket , type 0
Event Name: APPCRASH
Response: Not available
Cab Id: 0
P1: Studio One.exe