Submitted a song with three periods in the filename/title and it breaks the download link.

For reference:
http://battleofthebits.com/arena/Entry/the+alien...+its+a+train.mp3/27978/

It seems that a sequence of periods gets converted to a single period.

This download link does work:

http://battleofthebits.com/player/EntryDonload/27978/BotB%252027978%2520the%2520alien.%2520its%2520a%2520train.mp3

Dr. Slimeball diagnoses a case of implode(".", explode(".", $filename))

commas as well too iirc
maybe some other punctuation

it's been around for a while but hasn't been fixed