Hi Joni.
It looks like your workflow data is corrupted.
If you are a developer you can try the following. 1. Disable "Execute business logic in CIL" under your user options. 2. Rerun the tutorial, you should then be able to double click on the infolog to drill into the place where the error is being called. Place a breakpoint in the code there and debug what info has been corrupted and try clean it up in SQL