Comment 23 for bug 779932

To get better logging open the file config.mk in the compat-wireless sources you unpacked and change:
# CONFIG_RT2X00_DEBUG=y
to
CONFIG_RT2X00_DEBUG=y

then recompile and try again.

Anything in the logs (dmesg and /var/log/syslog) when things go bad?

Also, your last ping statistic is over only 3 pings. It may be better to let it run longer.

Where those bad results with power saving on? Contrast standard ping (with power saving on) with a much higher traffic ping (200KB/s) to _your_ router:
sudo ping -i 0.005 -s 1000 -c 1000 192.168.1.1