Instructions for screenshots:
What video card do you have? Have you checked that the video card drivers are up to date? A month or two ago there was a Hearthstone patch which introduced a new version of the graphics engine, which means the minimum requirements increased (and also which may explain why you now need to update the drivers if they are too old).
Minimum requirements are here:
There is also a link in there listing all the supported graphics cards.
If you need more help, you may have more luck in the Technical Support forum.