Remove any and all traces and remove any symlinks you manually created.
All that did was mess things up.
Use one of the following:
apt-get install flashplugin-nonfree or
apt-get install flashplayer-mozilla
Also check about
:plugins and see what plugin is being used. I am guessing you have Gnash installed. As root try doing:
update-alternatives --set flash-mozilla.so
You should also update your browser to either the version in backports or from the mozilla.debian.net repo.
Is your video card a nvidia card? There are known issues with nvidia cards.
Right click on a flash video and turn off hardware acceleration.
if none of the above work try searching Google or the debian forums at:
Do not manually move, create, delete any files or packages.