Update: These steps only work for the Vault 2011 version of the DLL. Go here if you are using Vault 2012.
A couple of people have had issues with the fact that Autodesk.Connectivity.WebServices.dll is unsigned. This is a problem if you want to sign your project. Visual Studio won't let you sign something if it references an unsigned DLL.
Fortunately, there is a trick you can use to sign the WebServices DLL. The trick involves SN.exe, ILASM and ILDASM.exe, which are .NET tools provided by Microsoft. You basically de-compile the DLL to IL code, then you re-compile with a key.
Example BAT file:
"%WinSDK%\sn.exe" -k keyfile.snk
If all goes well, you will end up with a signed WebServices DLL. The original DLL is still there, but it's been renamed with a ".1.dll" extension.
This trick will work with any .NET assembly, so don't let unsigned references prevent you from signing your project.