To use Twitter (update via wdtiwtter.exe), which uses oauth, as a security step, you need .NET 4.0 Extended install on your pc
Download .net herehttp://www.microsoft.com/net/download
You'll need one from the "Server and Development" list (don't know what CPU you have), not the desktop list.
It is a bit confusing because it shows as "extended" after it has been installed, but on the download page it's just "the one that doesn't say it's the Client version".
The you can click on setup oauth at the bottom of the twitter setup under control panel
then follow the instructions in the program that runs
you can reset that initial first time setup by deleting the files
twitteroauth.txt and twitteroauth2.txt
where WD is installed