i hpu the below links will help u
http://sinedax.blogspot.com/2012/02/ax-2009-ep-sysargumentnullexception.html
http://blog.walisystemsinc.com/2011/11/value-cannot-be-null-parameter-name.html
http://sinedax.blogspot.com/2012/02/ax-2009-ep-sysargumentnullexception.html
http://community.dynamics.com/product/ax/f/33/t/48820.aspx
http://community.dynamics.com/product/ax/f/33/p/62627/113480.aspx#113480
http://community.dynamics.com/product/ax/f/33/p/60614/111208.aspx
http://daxdilip.blogspot.com/2011/08/troubleshooting-dynamics-ax-2012-excel.html
thanks