changing wireless channel of your root router.
Reinstall the driver of the TL-WN821N (Uninstall the anti-virus software first).

I have the same problem with the TL-WN822N v2 on brand new windows 7 installation without antivirus program, with the latest drivers from the tp-link site (without the tp-link connection manager program - at least untill it stops bugging and minimizing windows).
It's connected to WR1043ND v1 router currently on channel 9 with the latest firmware installed again from tp-link website.
It's usually running properly but when I start downloading torrents and put some loads on connection - it drops.... showing limited access... and I cant even connect to the router config page, so I have to disable and enable adapter to reconnect.
And no ... reinstalling driver doesnt help as long as it's the same one... neither uninstalling anti-virus software (I dont have any)

Hi many thanks, I have done that and the diconnections seem less frequent. The other problem i have is that the window I am working on looses focus and I have to re-click again to be able to type, this has only happened since installing TP- Link software, again any help would be appreciated.