the solution is here and i am talking from experience. it doesn't apple to dota only but apply to most of the games. if u suffer a sudden drop in fps then do this.

1. most probably your laptop or desktop fan or heatsink is all clogged with dust. time to give it a good clean.
2. it's your graphic driver. always use the latest graphic driver and download it ONLY from your manufacturer site. never download it from any third party sites, torrent or anywhere else.
3. lastly, if all above is done and u are still suffering from the drop in fps in dota only and no other game, it's time to do a clean install of your warcraft. if it still happens to all other games, might be a bad capacitor in your mobo or your harddisk is showing signs of failing.

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