I wanted to fix the solution myself and tried to locate the registry key specified in the article, but was unable to locate it. Here is where they claim it would be:
HKEY_CURRENT_USER\Software\Policies\Microsoft\Office\12.0\Word\Security\FileOpenBlock
and here is where I actually found it:
HKEY_CURRENT_USER\Software\Microsoft\Office\12.0\Word\Security\FileOpenBlock.
Other than the minor error in the article, I was able of fixing the issue and of opening older file versions.
I am using Windows 7 Professional 32 bit.