Embedded QT media file not loading or playing in Safari half the time

I have been using the same HTML code without fault for years but in the past year or less I notice half the time it no longer loads and plays the file. This is in Safari only (which is odd, since it works in the other browsers like Chrome and Firefox, yet Safari and QuickTime are both Apple products). The only browser I usually ever have ssues with inconsistencies for viewers is Internet Explorer on Windows (no matter what site I am creating) but recently, although I'm using the correct coding (same as for years and even double-checked to verify) lately the song on my site only loads about half the time in Safari 5.1.8 on Mac OS X 10.6.8. This started almost a year ago I believe. Here is an example of my HTML code (using both the OBJECT and EMBED methods for maximum browser compatibility and consistency):

<p><center><OBJECT CLASSID="clsid:02BF25D5-8C17-4B23-BC80-D3488ABDDC6B" HEIGHT=25 WIDTH=475 CODEBASE="http://www.apple.com/qtactivex/qtplugin.cab"><PARAM NAME="src" VALUE="http://www.mysong.mp3"><PARAM NAME="autoplay" VALUE="true" ><PARAM NAME=“loop” VALUE="true" ><EMBED HEIGHT=25 WIDTH=475 TYPE="video/quicktime" PLUGINSPAGE="http://www.apple.com/quicktime/download/" SRC="http://www.mysong.mp3" AUTOPLAY="true" LOOP="true"/></OBJECT></center>

Sometimes instead of playing it just displays the faded "Q" logo with a question mark? There seems to be no rhyme nor reason when and if it works or not and it is also the case when I test it on an HTML practice board: when it works it works on both the practice board and my site and vice versa; when it doesn't work on one it doesn't work on the other either, so it's not a site issue. Could it be some corrupt Safari-related file on my computer?

UPDATE: I just checked and it also plays fine on Safari 4.1.3 on an old iBook G4 running Mac OS X 10.4.11 Tiger, so it is definitely something with my version of Safari 5.1.8. I'm guessing it may be a plug-in (not used in Safari 4) that is interfering intermittently? I just tried deselecting "Block Pop-Up Windows" and it works now, but that could be a coincidence since it occurs sporadically anyway. If I continue to have the issue I'll test it with all plug-ins disabled and then try to isolate it, but If anyone has any tips or hints I'd much appreciate it, thanks!