Symptoms
After migrating the servers to the DR data center, some of the forms (in the SmartForms Runtime environment) were displaying blank with a small rectangle. There were custom themes on some of these forms.
The following error was caught in host server logging:
2025 Error Marshalling SourceCode.Forms.Runtime.ClientServer.GetFormAx, Theme '?' not found
Diagnoses
The custom theme being used had not been registered.
Resolution
Custom themes need to be registered on a given server where they are in play
http://help.k2.com/onlinehelp/k2smartforms/DevRef/current/default.htm_Deploying_and_Registering_Custom_Themes.html