ACAD Map 3D 2011 running slow

[Anonymous]

System Information:

Win 7 Pro 64-bit
AutoCAD Map 3D 2011 x64

Hardware:
Core i7-920
9GB Ram
1.75GB GeForce GTX 260 Video Card

When working with a 12MB drawing file a process such as erase is taking 20+ minutes to complete (200k objects) where on a lesser machine with WinXP and Map 2009 it takes seconds.  We have gone through dozens of suggestions including turning the overclocking off, 3D accelleration enabled and disabled, running NetFramework 4.0, turned off virus scanners, etc...  I am seeing a lot of reports of this but no real solutions or answers as to what may be happening.

I can run this same file on a laptop with WIN 7 Pro 32 and Civil 3D 2011 and it runs fine.  Is 2011 not truely 64 bit compatible perhaps?  Any ideas or help is greatly appreciated.