Thanks for sharing the Maya scene file.
Unfortunately, I didn't had Maya 2012 but I checked this on Maya 2013.
Although, I didn't have enough time to look inside the Hypershade and Dag Nodes, but here is what I learnt from the render file log.
1 The render log seems to have "cycle on" warnings associated with different node attributes, e.g. "shell_trailShape.ageNormalized" can you confirm if this attribute is connected? As I didn't checked the User Defined scalar and vector attributes connected from particleSampler info node.
2 'Hardware rendering selected but skipping'- is what I get while rendering, although the scene is being rendered with S/w renderer.There might be some dependency on the Hardware Renderer Dag Nodes.
Can you confirm if these are the messages you are getting in the render log?
If yes, than in my opinion reconnection of Shaders,nodes etc. while making sure there is no cyclic depedency in the Node connection and trying deleting "HardwareRenderGlobals" nodes from outliner should be the first few steps to Diagnose the problem.
Attached is the Render log snapshot of warnings.
I hope I didn't sound trivial, in case your issue is resolved please share the solution.