First of all, I feel sorry that the Optimizer 6 brings you trouble you described.
As you described the problem only happens during midday, my initial thinking would go to any scheduled jobs. It may be some jobs competing resources with the Optimizer causing Toad frozen. If you have any Windows job scheduled at around the same time, you may try reschedule them to a different time to see if it solved the problem or changed the time the problem occurs.
And alternatively, I suggest you try the new version of SQL Optimizer version 7.3. This version is a standalone version that can run totally independent of Toad. So in the worst case even if the Optimizer 7 still hanged, it would not affect your Toad session.
Let me know if you have any further questions.
Message was edited by: Alex Luk