[X4U] Sound output suddenly changes! Ugh!

[Crandon David]

Hello Everyone,

For a friend of mine, below are his symptoms. Could you please all  
help out? This is a spontaeous change and it appears nothing in  
particular caused it....

Thanks.

the audio problem with video clips, which for no apparent reason came  
upon my mac a few weeks (?months) ago, drives me nuts.

Here is a summary of the symptons to make it easier for you to post  
this in one of the mac forums you visit. I would really appreciate  
it. The problem has nothing to do with specific preference settings  
of various softwares (WM-player, QuickTime etc) or settings in system  
prefs > sound > output.

The audio portion of certain video formats does not play through  
external speakers anymore but only through the internal built-in  
speakers:

mov and avi: sound plays ok through external speakers both in  
QuickTime and Preview.

mpg: audio only from built-in speaker, both in QuickTime and Preview.

wmv: audio only from built-in speaker (opened with WMPlayer)

Mac start-up sound audio only from built-in speaker but all other  
alert sounds also from external speakers.

All audio files, mp3, aiff,  iTunes etc play through both int. and  
ext. speakers according to the settings in system prefs > sound >  
output.

Mac Pro, 2x 2.66 GHz Dual-Core Intel, 2 GB, OSX 10.4.1