Symptoms
K2 is throwing a SQL error "Incorrect Syntax near the keyword WHERE". Not sure how to debug, since the SQL is generated behind the scenes.
Diagnoses
A good place to start is to review the Action that triggers the error. In this case a Buton on a Form. Once identified which triggers the error, reviwing the rules is the next step. If there is something missing in any rule a word with a dotted line under will be visible.
Resolution
One of the rules for a SmartObject was missing an identifier (WHERE clause). Adding the missing property resolved the issue.