Hi Tom,
It is possilbe that you log in Vault 2009 server via AutoCAD Civil 3d 2010. You can check the version of your AutoCAD Civil 3d. AutoCAD Civil 3d 2010 should log in Vault 2010.
Hope this helps,
Yuki
Edited by: pingyong.zhang@autodesk.com on Nov 11, 2009 9:49 AM