I had this same issue.....upgraded to 7.6...no audio when previewing movies....wrote to apple, they said remove and install the standalone quicktime....didn't help...i removed and reinstalled itunes...didn't work..they said they were working on it and would get back to me....that was yesterday...realized today that all my stuff that i already had i also couldn't hear on videos....music worked fine, but no sound on videos....found a site that had 7.5:
http://www.soft82.com/get/version/download/windows/itunes-7-5/
removed itunes and quicktime and installed 7.5...kept getting the error that said "iTunes Library.itl" was created by a newer version and it wouldn't open....did a search, and found this string and linked to this article:
http://docs.info.apple.com/article.html?artnum=93732
once it said the library was just for playlists and other stuff and only used for iTunes i decided to delete every one that was in my computer.....7.5 was then able to open....of course my library was empty....i then went to file/add file to library and selected my music....it's having to add everything that i had....(and it's still in process as i'm typing)...but i'm hopeful that this is working!!!
Just finished and it worked....i have audio back on my videos!!!! Sticking with 7.5!!!!
Message was edited by: stompki1