acShellExecute("open", "http://www.google.com", "", "", 1)
Works here on a recently updated win7x64.
In your case I'd try to check it by running a portable StrokesPlus and if it's okay then there is probably something wrong with your settings file.
Or if you on Win8, see this thread for a temporary fix: http://www.strokesplus.com/forum/topic/924/windows-81-update-problems