Certainly you are not in cause, photons !Did i do something wrong.?
What operating system are you running Maya on ?
Try activating the sun/sky through the shelf instead, then start the Palette and see if you can switch env modes safely. There are tricky things happening into the Palette if you switch to sun/sky without having created a sun first, actually managing the case.
Does this crash Maya for everyone ?
Note that the resulting directional light is locked toward the center of the scene, it must be moved around to define the sun position. I will probably release this constrain soon.
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Added cycle support for mesh instancers, now one single particle system can be used to instance an arbitrary number of meshes. Rotations and expressions not supported yet, will be in the next release (FEB10 brand).
I'll post a few images as soon as I can get enough RAM for Maya to compare versions