Slow selection in asssemblies

I'm having issues in assemblies when selecting components in the Feature Manager design tree.  The problem seems to be independent of the size/number of components in the assembly.  What I'm trying to do is select multiple parts in the assembly design tree (to regroup them into a folder or change whether they are displayed on the BOM, etc.).  Sometimes I can select 20 or more components and the response is immediate.  At other times I can be selecting as few as two or three components and the computer grinds to a halt (I just get the spinning circle).  It's not tied to any one assembly or computer (my co-workers have the same problem).  I wait (sometimes as much as minutes) until the selection is complete.  If I'm having the problem, then after the selection is complete it continues to be slow when I right click for the menu to do the next step (e.g, add to new folder).

The assembly is on a network drive and we are using network licenses.  However, during these times when the computer gets slow, my network monitor shows little or no network activity.  Neither the CPU or memory is at maxed out during this problem according to the CPU/memory monitor I have running.

I've made sure there are no errors in the models or assembly.  I've tried combinations of rebuilding, saving, setting lightweight, setting resolved, etc. with no luck in figuring out what is going on.  Any ideas?

SW 2010 SP 4.0 (will be upgrading to 2011 SP3 hopefully soon)

HP xw8600

Windows 7 64 bit

Intel Xeon X5450 3.0 GHz 4 Core, 4 Logical Processors

4GB Ram

Video Card NVIDIA Quadro FX 4600/PCI/SSE2     Driver:  8.16.11.9156 (SolidWorks Rx says this is okay)

SolidworksAssemblies