Hello -
A trick you can use to try and identify problem you are having using the Workflow deisgner is to turn on the JavaConsole for the designer session. On windows you can do this by modifying the shortcut to start designer. Add the following parameter to the end of the path:
"c:\wf\adobe_livecycle_workflow_7_0_designer.exe" -is:javaconsole
Note the Quotes around the path, and the parameter after the quotes.
This will open a console window along with workflow designer - any exceptions thrown will print a stack trace here (as well as any System.out lines you use in a QPac Dialog etc.) I would recommend using this option all the time as it may help diagnose issues.
In the case if mis-matched versions on the server and client you can expecct errors like "InAuthenticPrincipalException", "InvalidClassException" or SerialVersionUID mis-match.
Hope this helps,
Will
