PC gets choppy when router runs in 40 mhz mode

Question

This is really odd but I have a e2000 router and a wmp600n wireless card in my desktop pc.  Everything works fine until I enable 40 mhz for faster speeds in the e2000 router.  When I do this the router switches from 20 mhz to 40 mhz and I get the faster speed.  But the effect of this is that my pc gets all "choppy".  What I mean is that everything freezes up every few sec.  For example when im minimizing windows, the windows freeze half way for about a sec then unfreezes.  My mouse does the same thing, even my sound is choppy.  Anyone else have this probelm?  I have to switch my router back to 20 mhz and then everything is fine again.
Using windows 7 64 bit
Using newest dirvers and firmware from linksys

Answer 1

OK so ive done a little more research on this and seems  A LOT of other people are posting exact same problem as me.  Here is even a example of a post from here.
http://homecommunity.cisco.com/t5/Wireless-Adapters/Installing-drivers-for-WMP600N-makes-my-system-s...
Looks like people are calling the effect stuttering from the drivers.  Anyone have a fix?