make sure when you install the plugin, you uninstall, reboot, then install it from the website again.
Go to "Control Panel\All Control Panel Items\Programs and Features"
Uninstall "Adobe Flash Player 10 Plugin" and "Adobe Flash Player ActiveX"
install new ones from web.
for good measure you can also try uninstalling java and reinstalling that too.
to eliminate any other variables you should try deleting history cashe, and any cookies