You should first uninstall any previous version of Flash Player, using the uninstaller from here (make sure you use the correct one!):
http://kb2.adobe.com/cps/865/cpsid_86551.html#prob1=uninst,os=m10.6,
Download this if you haven't...
http://fpdownload.macromedia.com/get/flashplayer/installers/archive/fp10.1.102.6 4_and_9.0.289.0archive.zip
Once downloaded if it doesn't unzip automatically the double click on that file.
Look for the fp10.1.102.64_and_9.0.289.0archive folder, open it, look for the Flash Player 10.1.102.64 folder & open and look for 101r10264 folder & open it, double click on the flashplayer101r102_64_ubmac.dmg file, choose the Install Adobe Flash Player file to install... they don't make it easy! 😟
Or I put up the smaller ones here...
http://dl.dropbox.com/u/450421/flashplayer10_1r82_76_ub_mac%20copy.dmg.zip
Stand alone player...
http://dl.dropbox.com/u/450421/LastFlashPPC.zip
Or free 3rd party...
http://www.wimpyplayer.com/products/wimpy_standalone_flv_player.html
The last really supported Flash for PPC was 10.1.102.64, but if it's for like Facebook or such, people have been fooling FB to think they have a later version installed.
Texas Mac Man's Flash hack/post...
https://discussions.apple.com/thread/3599648?tstart=0
See in each Browser which version of Flash it thinks it has...
http://kb2.adobe.com/cps/155/tn_15507.html