In case anyone else runs into this problem, this is what it took to resolve:
- Shutdown the Web Help Desk service
- Launch SQL Management Studio
- Modify the local admin account IAW http://knowledgebase.solarwinds.com/kb/questions/4600/Re-Activating+the+default+admin+account
- Set the WHD_License_Key to NULL under dbo.Preference
- Copy and Paste the new license key from the web site
- Start the Web Help Desk service
- This caused an Invalid License Key page to be displayed when the service was launched on the localhost (remote connects got a maintenance notice)
- Copy and Paste the new license key into the text box and hit Save