I'm having problems when I want to use more than one CPU to render with mental ray. I'm having this issue with standalone 3.9 and 3.10, as well as with mental ray for Maya 2012. mrforMaya2011 seems to be okay.
If I kick off a non-iray job in mental ray standalone 3.9 or 3.10, it'll run for a while, then segfault. The segfault doesn't occur at the same place every time - sometimes I'll get several frames rendered and sometimes it happens during the first frame. Nor does it always segfault at the same place in the render process - sometimes it's during final gather, sometimes during the rendering, sometimes other. (iray is working well in 3.9. I'm having a separate issue with it in 3.10, which I may detail in a different post, after I look into it a bit further.)
When I render within Maya 2012 with mental ray, and specify more than one CPU, the whole program freezes up at some point during the render and I have to kill Maya from the command line. The progress reports "RCMP Info: flushing 32484 bytes" over and over again until I kill the process.
I'm on a Linux 64-bit platform, 96 total CPUs. So you can see why I don't want to use them one by one. =)
Any ideas as to what may be happening?