1. Press Start and type "Run"
2. In the run command, type "%temp%"
3. Search for www.minecraft.net
4. Delete folder
5. Load minecraft.net
6. Enjoy Minecraft!
If this doesn't work I'll try and find another way, so tell me if it doesn't, but it should work.
This is also in the wrong section, it could have gone under off topic or maybe Minecraft Discussion.
My friend had the same problem 2 days ago. He used internet explorer and I told him to use Google Chrome, and once he changed it worked fine. So try to use another browser, maybe it'll help. If not I'll look to see what else I can find that might help.