DCTranscriber

When I try to play certain audio files, I get an error message stating that the avutil-51.dll file is missing. Eventually, the audio file does upload, but that message is annoying, and it freezes my computer until the file is completely uploaded. Does anybody have this problem, and if so, what did you do to remedy it? I did a google search and some hits came up as this "avutil-51.dll" file is a virus of some sorts. I have Norton virus protection and haven't encounter any problems. Again, this only happens with certain audio files, not all audio files. Please advise. TIA!