Just curious and I'm assuming you're using Flip4Mac when opening a wmv file in Safari, but how do you know the wmvs are being opened with QT 10??
And I'm not sure that Flip4Mac even uses QuickTime X Player as it had trouble with that version and one needed to install the optional QT 7.
Have a read at:
Telestream Flip4Mac - Support - FAQ
"OS X 10.7 Lion: mms and Windows Media based web streams don't play in Lion's QuickTime X 10.1 Player.
This is an issue in QuickTime X Player in Lion. Please download and install QuickTime 7 Player. QuickTime 7 Player gets installed in /Applications/Utilities/ and can be used in parallel to QuickTime X. Select a WMV file in the Finder and open the Get Info window to assign it to QuickTime 7 Player. Select QuickTime 7 Player in the "Open with" dialog, then click the "Change All…" button. From now on QuickTime 7 Player will open all WMV files including web streams.
OS X 10.7 Lion: WMV files only show black video in Lion's QuickTime X 10.1 Player.
This is a conflict caused by the 3ivx codec. Please go to your ˜/Library/QuickTime/ folder and remove the 3ivx codec, then restart all QuickTime applications and web browsers. ..."