metlica,
While trying to download your song ESET gave me an error...your file has a virus. This is common with .wma files moreso than .mp3
It could be that some but not all your .wma files have trojans hidden within them.
The Trojan was:
Win32/Getcodec.A - CA
This could be the source of your problems.
Note that the virus could be in all or most of your .wma files. That is one reason.
I would scan for viruses, and especially see about removing the codec virus.
Once that is done, try the songs again. And also try re-encoding them again as that may work.
Note that some songs may be dummy songs and may never play, some record companies do this on purpose. You should scan your PC thoroughly for viruses.
If you don't have an antivirus already installed, try AVG Free and make sure its up do date