I received the error: Could not initialize Prizm Viewer control because an internal error occurred when I double-clicked on a file type associated with Prizm Viewer. What might cause this?

Some third-party virus scanning programs disable Prizm Viewer from running in Internet Explorer. If you use McAfee VirusScan, for example, the Properties of the Access Protection task contain a Category called Common Standard Protection. Unchecking the Block action for the Rule titled Prevent common programs from running files from the Temp folder will allow Prizm Viewer to start.