well if things were working fine for you until recently i don't see how it could be a hardware issue unless something has broke, but in that case you'd probably be experiencing other issues too.
I personally think it's probably a flash issue, i've had issues where I've upgraded flash and its made videos unwatchable. Adobe can't test for every possible hardware configuration. You say you've never updated it, but you're on the latest version of flash, that means its updating automatically. Uninstall flash, and
http://helpx.adobe.com/flash-player/kb/archived-flash-player-versions.html#Flash%20Player%20archivesinstall the one from second to the top of this list "Flash Player Archives"
(Released 9/9/2014) Flash Player 14.0.0.176 (120.37 MB)
you'll get a zip file with a bunch of other files cause its meant for developers. but all you need to worry about is running the flashplayer14_0r0_176_winax.exe file.
if it asks to update automatically don't let it. choose ask me to update or dont update at all. but remember to update at a later point, its important you do. sometimes flash updates contain security updates.
i've never used netflix but looking at their site it does use silverlight, so i dont know what to say about that, but its worth trying to install an older version of flash.