Are you running any applications like Synergy or TeamViewer or something that may be stealing focus? I don't want to cause a panic, but I've even had one guy find a key logger that was intercepting input (this is just one isolated case, but it illustrates the countless things that can be going on in Windows). You might want to look in your install history and see what has changed, because something has changed and if VA just decided to stop working in that regard (commands recognized, nothing happens).
Also, be CERTAIN you are running as an administrator, as that is a very common item to look out for.
Hope that helps!