You know, I have encountered this problem a few times when doing my Dogs of War scene, with 5 popualtions with image heavy objects, and I have a fairly simple solution that allmost certainly will work!
The problem is, the 11 popualtions use a lot of RAM, like Matt told us.
"Unable to allocate pixelmap: size 12960000 bytes" as far as I know means there are large texture maps that don't fit in the memory anymore. When ram is full you get the unable to initialise rendbuffer because the bucket is full.
What kind of populations do you use? Trees? Do some of them use the same textures? If so, copy the default shaders in question to the main node view, and copy their names into the shader space in the multi shaders, like in the attached image.
If you have illiminated enough images you might be able to render, if not, you have to resize the textures, and perhaps save them at lower compression quality.
This has deffinately worked for me, I hope it works for you as well.