Arpit, are you able to produce this error on the sample Dynamics AX 2012r2 sample image Enterprise Portal.. If so, I'd love to to know so I can try to debug it.
But if not, here is what you need to do in order to solve it:
This is a case for WinDbg. When you really need to debug what is happening on Dynamics AX, nothing (that is free) is more effective. It's what Microsoft uses for their support team to do the heavy duty debugging. Thankfully,
their support team made a blog post showing how to use this feature for Dynamics AX.
blogs.msdn.com/.../setting-up-windbg-and-using-symbols.aspx
Can you post the dump file and the symbols from this?
I'd do it myself but I'm not on your installation. However,the tutorial is very straight foward and written well by Microsoft support. That will tell us the cause of this.