Is this an animated render or just a still image.  If it's a still image select "One for all frames" under the irradiance map.  And if you don't need it, turn off skylight.  That's for outdoor scenes mostly.  Your indirect lighting settings themselves aren't all that cranked.  I almost always use the Improved edges and light through transparency settings.  I don't think I have yet to run into a situation that I needed to use Shadow Compatability mode for.  I usually don't use depth of field either.  I only have 8GB and I run all of the other settings at max.  I commonly use large texture maps.  But I very rarely hit this error now.  I do use C 8 Pro though, and it is a lot more stable.