My Macbook Pro won't play sound with some applications

Today I downloaded some WMP clips (as I've done before) but when I went to play them a message popped up which read, "This file may not play correctly because it was compressed by using a codec that is not supported"....
After clicking okay on the message, the video image displayed normally but there was no sound.... so I thought whatever, there must have been something incompatibility issue with that particular clip, but then I realized that my yahoo messenger was also mute as well as an X-plane application I had opened.. The sound for other applications like I-tunes and I-chat worked normally...
The same problems remained after a shutdown/reboot.. I then went to the powerbook technical page and it had asked me to make a change in the "Audio Output" section of the "Audio MIDI Setup" but when I opened it there's a message in the Audio Output section which read "Output is not Supported"......
Before calling technical support, I thought maybe one of you could provide some insight... I really appreciate it...
Eric....

sorry, can someone move this thread to the macbook pro forum.... Thanks
Eric...

Actually I found the fix via a search on this informative website...
From what I read, the fix is only temporary.. Why is that? Was this due to a glitch in TIGER and is there a permanent fix yet?
Eric...