Filing a ticket is probably your best option with this issue tbh as there are so many variables. All I can say is that both 3Delight and IRay are both pretty stable on my system and both will render no matter the type of material presets applied.

This may be a bit 'try turning of and on', but have you tried resetting the render settings to default for 3Delight just in case something was changed at some point that could be causing the issue?