I keep on getting this error message when trying to run a simulation and I have no idea why.
Btw, your picture is showing your 2.76 Blender version (in the error log), but you are not saying much about which simulation, if you built it, or if you get it from friends, websites... it could be a buggy file, a buggy simulation, or not compatible, somehow, with your blender version (eg: it could be a very old file)... it could be pretty much anything... help others help you giving some more info about how and where this is happening...
Anyway (again from the error log) it seems to use a "cellblender" addon, though. Did you have that addon installed? It's not in Blender by default... but if it's there it could be a different version from what your simulation expects (maybe an oldaddon version), or it has some bug...
I guess it is this:https://github.com/mcellteam/cellblender (related to http://mcell.org/): "CellBlender is an addon for Blender (2.6x-2.7x) to create computational cell biology models for use in MCell and potentially other cell simulation biophysics engines"
It could be needed to update the addon, or your Blender version, too. Version 2.78 is the latest in the 2.7x series.
edit: I just installed mcell and cellblender, using latest blender 2.78 on my Windows 7 desktop pc, and then followed the "first time running" steps
after which I ran this very basic tutorial, http://www.mcell.psc.edu/tutorials/single_molecule_diffusion.html
and it seems to work:
Maybe you can download and install a fresh new Blender .zip file (so you can keep the one you have installed), and double check to follow all required steps...