Here is an alternate installer that should work. I tested this even in the "Program Files" folder. The original installer failed when converting some files before packing them into the pff which means some files were missing. This should fix that. I loaded up some maps (OMG memories!) and they all worked perfectly. I even played on one by myself for 20 minutes
MOST people should already have the .NET Framework v4 installed. It comes pre-installed on Windows 7 SP1 and higher. If you have Windows XP, download the .NET v2.0 version if you don't have .net framework v4 installed.
Windows 7 SP1 + (.NET Framework 4.0)
http://www.mediafire.com/file/a8jd9c...ller_net40.exe
Windows XP (.NET Framework 2.0)
http://www.mediafire.com/file/so9lth...ller_net20.exe
If you have Windows 7 without SP1, download the 2.0 version.
Please let me know if this works for you!