This problem Might be cause by your anti Virus Protection Program,
You might wanna turn it off, when hacking.
This could also be your firewall.
Update to the latest .net Framework 4.0
If you haven't
That doesn't work for you.
Use another injector.
There is plenty out there.
You can give my injector a try if you want.
But Ryski's Injector works fine with .net Framework 4.0