An out of memory error indicates just that that particular operation exceeded the available memory, but it's not necessarily that operation that was excessive.
In this case, 65484 bytes is tiny, so somewhere else is hogging up the memory and it could possibly be somewhere in the plugin... or it's the plugin is the straw that broke the camels back.
256MB is a huge amount of available memory, and I can't see the plugin consuming all of this.
I would feel that I'd have heard more stories by now if the plugin was consuming 256MB+ as that would kill of most shared hosting sites.
Keep me posted!