When an unrelated newly downloaded application hung at launch, I remembered Handyman's "problems on Leopard with auto-update due to the stupid Leopard 'are you sure you want to launch' dialog."
I decided to Restart 10.5.4.
Now both OmniWeb 104805 and the other new application launch fine after I respond to the "stupid Leopard dialog."
Never mind.
[submitted as formal feedback]