Two months ago I blogged about building plug-ins for DriveWorks, unfortunately a couple of people have tried the tutorial since we shipped SP1 and had less than stellar luck.
The bad news is we made a bit of mistake with one of the configuration files we shipped in SP1 which causes problems for plug-ins. Sorry :-(
The good news is; it is really really easy to fix, just download the following zip file which contains one file called "DriveWorksAdministrator.exe.config":
http://www.philipstears.net/driveworks/SP1ConfigFile.zip
To apply the fix, just overwrite the file of the same name in your DriveWorks installation directory, e.g. "C:\Program Files\DriveWorks\6.1\Administrator\" and the next time you start DriveWorks you'll be able to load your plug-ins :-)
The other good news is that this issue is fixed in SP2 which will be shipping very soon now.