I noticed this bug in SQLYog 4.2 RC2 and it remains in 5.01. I run a query, then select my table in the Result pane drop-down so that I can edit the results of the query. Then I click within a field and select some text. Now, if I highlight my query again with the mouse and hit F5, SQLYog crashes. Instead of highlighting my query again, if I just place the cursor within the query and hit F5, the query runs again and it works fine.