Quick Time question mark keeps appearing

I've had nothing but trouble with Quick Time since I updated to 7.3 about a month ago, after getting an automatic prompt on my machine (Intel iMac 2 Ghz, with OS 10.4.11). I sometimes get the big Q with a question mark when the Safari browser goes to a page with video. It often corrects itself when I shut down the browser and start up again. What to do? Is this what Apple considers an "improved" update of Quick Time? I wonder if it has anything to do with running other codecs. I noticed that the question mark thingy happened after I had been running VLC.
TIA for any insights into this.

I am replying to my own inquiry. Obviously no one seemed to have a suggestion for me, but as it turns out I solved the problem myself so the info might be of help to others.
The failure of the Adobe Flash plug-in had nothing to do with my VLC codec. I removed the plugins for the DiVX that I had in my folder, and that has allowed Flash to work properly. Curiously, judging by the multitude of web entries, there are many people with the Intel iMac, running a recent Quick Time, that have problems with their browser failing to run the Flash program for certain online video clips. It seems that various other solutions have worked for the problem, such as disabling 'Flash' settings in Quick Time's MIME options list.