And yes, this error occurs more often than not, the only difference with this scene is the dynamic cloth.
If it's a random crash, it is most likely a graphics card hardware fault, although it could be some sort of corrupt geometry too. Is the error always at the same line number? If you can post or send me the octaneplugin.log and cuda.log files after this happens then I can see what is causing it. If you have a small scene that causes the crash, can you email it to me pls?
Is this thing really gonna work for greater than one character and one prop in a scene, unless I can somehow get 16 terrabytes of RAM on my video card?
My 1 Gig card will do 4million polys no problem. Are your scenes 3 times larger than that? Your limit will be the texturemap slots - which on the 500 series is only 64 RGB and 32 grayscale. So use the scene texturemap count script (or Image File Statistics button) to ensure you are within limits.