It looks like that something is wrong overall. Even the official demo version from MS page freezes upon opening, giving out the very same result (uh, Samuel, you told me it doesn't requite JAVA, yet it still opened in JAVA).
If it is caused by Net 4.0, I'm going to have a pretty bad time uninstalling and installing everything again.
Edit: Installed and reinstalled Minecraft; stuck on Mojang logo. Upon focusing on the window - program stopped responding.
I'm pretty upset right now, since it is looks like that Mojang made Minecraft requiring OGL 2.1 (I have 2.0) for some odd reason. It means I need new graphic card what will not happen, because there's no logic in upgrading my piece of junk - and I will be likely buying new PC in next quarter.
Mojang and Microsoft, I'm pretty disappointed into you both right now.