Version:           2.2-Git (using KDE 4.3.4)
Compiler:          cmake 2.6-patch 4 
OS:                Linux
Installed from:    Ubuntu Packages

When trying to play an MP3 with a #(%23) character in the file path the file will be skipped.  As far as I know this has not been an issue in the past.  I am using the Phonon Xine backend.  Here are some snippets from the debug log which illustrate the problem:

amarok:       BEGIN: void EngineController::playUrl(const KUrl&, uint)    
amarok:         [EngineController] URL:  "file:///home/cparkins/Music/Chevelle/Point%20Number%201/Chevelle%20-%2002%20-%20Point%20%231.mp3"
amarok:   [EngineController] [WARNING!] Phonon failed to play this URL. Error:  "11:57:40 AM: input_file: File not found: >file://home/cparkins/Music/Chevelle/Point Number 1/Chevelle - 02 - Point < "

Looking at existing bugs, this may be a Phonon issue, but there is something fishy about the error and how the file name is being cut off.  I am using phonon-backend-xine 4.3.1-4.  A workaround to this issue is to remove the # characters from the file name.