Have you tried running it from different websites? (probably won't work, but if you've tried everything else, why not give it a shot).Supermechs.comNewgrounds one
And just to double check you deleted the flash cookies properly, did you do this:
>Right click on the game, choose 'global settings'
>'Storage' tab >'Local Storage Settings by Site' button
>Scroll down to 'supermechs.com', select it, then choose the 'remove' button