Your pastebin implies, because of the timestamp, that the driver doesn't load on boot. It may be blacklisted as a part of the process to install ndiswrapper. Check:
gksudo gedit /etc/modprobe.d/blacklist.conf
Use nano or kate or leafpad if you don't have the text editor gedit. Is the line blacklist ath9k_htc listed? If so, remove it. Proofread carefully, save and close the text editor.
Next, please try, in a terminal:
echo ath9k_htc >> /etc/modules
Reboot. Any improvement?
You may be able to improve stability by checking the settings in the router. WPA2-AES is preferred; not any WPA and WPA2 mixed mode and certainly not TKIP. Second, if your router is capable of N speeds, you may have better connectivity with a channel width of 20 MHz in the 2.4 GHz band instead of automatic 20/40 MHz, although it is likely to affect N speeds. I also have better luck with a fixed channel, either 1, 6 or 11, rather than automatic channel selection. Also, be certain the router is not set to use N speeds only; auto B, G and N is preferred. After making these changes, reboot the router.
If these changes are ineffective, you might try a driver parameter:
echo "options ath9k_htc nohwcrypt=1" > /etc/modprobe.d/ath9k_htc.conf
modprobe -r ath9k_htc