Tom,
I haven't seen this error before.
Looking at the stack trace, it seems like it's failing to decrypt the password for one of your ArcGIS Server connections. Can you try opening up the file in an XML or Text editor and comment out the section with the node arcgisServerConnections and then trying to re-import the configuration?
-Javier
PS Would you mind sharing the configuration with us to so that we can try and figure out what's going on?