Version:           3.5.2 (using KDE 3.5.2, Kubuntu Package 4:3.5.2-0ubuntu5 dapper)
Compiler:          Target: i486-linux-gnu
OS:                Linux (i686) release 2.6.15-20-386

Anything that's opened through system:/home won't play in amaroK, probably one of KDE's most prominent applications. amaroK says "the local file doesn't exist". According to a a helpful post to the kubuntu-devel mailinglist:

"The reason it doesnt play in amarok is that because KIO does not allow seeking 
in files (you have to read them linearly), so amaroK does not use KIO. For 
system:/media it works because they use dcop to ask kded where the mount 
point of the device is. It would be possible to do the same for system:/, but 
like you say its a useless abstraction."

Submitted as a Konqueror bug since it does not only affect amaroK but non-KDE applications as well and the problem isn't amaroK's lack of support for system:/home but system:/home itself.

I'd just suggest to remove system:/home and put /home/user in place instead.