hye, Im suffering from the same problem as you. Using same wireless adapter aswell. DWA-110. ( which i think is the problem )
I dont think Its my computer, since i tune it to high performance.
Rampage2ex Mobo
Intel i7 920
GTX280 GC
6GB ram

So i dont think its my system, since i tried alot of games and they never lagged.
I dont think its the router or the modem, coz my brother is also playing dota on the same network, with a lower system, except for his wireless receiver which he uses a pci wireless receiver.
So im putting the blame on my wireless adapter. What do you think?

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Added on July 24, 2010, 12:47 pmowkay solved it. I bought a 10 metre LAN cable. Remove my D-Link wireless adapter. CPU - LAN - ROUTER.

And TADAAAA, now its lag free, no spiking. Its the wireless i say.

This post has been edited by mx007: Jul 24 2010, 12:47 PM