Laptop is Dell XPS M1710 , 2 GHZ core duo ,4GB ram.......blah blah blah
OS is windows XP pro SP3, all latest updates...
PCIe card is Gigabyte GN-WI06N-RH {AR5418 chiset} latest drivers from gigabyte.
DIR-655 firmware is 1.21 from Dlink
used as a access point, not a router, nothing on Wan port.
Mixed mode 802.11n,g,b
auto channel
auto power
security is WPA-personal, wpa2 only ,AES
dir-655 logs have nothing relevent , unless your interested in who connected and a long list of my sons WII connecting a lot.
When channel width = 20 MHZ , no problems detectable.
When channel width = 20/40 MHZ , problem is prevalent.
Again , problem only shows up on channel width = 20/40 MHZ , and large and constant data stream of a large file.