Check in IE10, tools, manage add-ons, under 'show' select 'all add-ons', you should see Shockwave Flash Object. Version should be 11.3.376.12
Flash is now a third party component of the OS and will update automatically via Windows update. Possibly updating the IE version of flash has upset the apple cart.
Run IE without add-ons, mouse cursor to bottom left and right click. Select run and paste iexplore –extoff . IE 10 will open without add-ons. Enable flash, for a while, to see if you get the same problem. If not then it could be another add-on.