Interesting worksheet. The issue is reported by the call to "mod(accnts, hdiv)" function inside the definition of "Evolve". I am looking into the details what would be triggering this specific message. I'll let you know what I find out.
To find out the root of the error:
1) Recalculate worksheet (this is only necessary once after you opened the worksheet).
2) On Calculation tab, click on |< (red VCR buttons) to trace to first error in the chain.
Hope this helps,
--Jakov