I have been using the 2.6.35 kernel with rt2x00 for about 6 months on an A100 card and hostapd. It has been extremely reliable.
After putting it off for a long time, I finally upgraded to Ubuntu 11.04 which brought in 2.6.38-10. Now I get errors and complete stoppage of the wifi card at least once daily. I've been rebooting to recover which is annoying.
0a09.0 Network controller Ralink corp. RT2800 802.11n PCI
Error in syslog
ug 10 230712 boxster kernel [ 527.088460] phy0 -> rt2x00queue_write_tx_frame Error - Arrived at non-free entry in the non-full queue 2.
Aug 10 230712 boxster kernel [ 527.088464] Please file bug report to http//rt2x00.serialmonkey.com
Aug 10 230715 boxster dnsmasq-dhcp DHCPINFORM(wlan0) 192.168.20.15 0024d67d6528
Aug 10 230715 boxster dnsmasq-dhcp DHCPACK(wlan0) 192.168.20.15 0024d67d6528 ihqc
Aug 10 230718 boxster dnsmasq-dhcp DHCPINFORM(wlan0) 192.168.20.15 0024d67d6528
Aug 10 230718 boxster dnsmasq-dhcp DHCPACK(wlan0) 192.168.20.15 0024d67d6528 ihqc
Aug 10 230746 boxster kernel [ 560.837561] received mDNS IN=wlan0 OUT= MAC=01005e0000fbf81edfdee7fb0800 SRC=192.168.20.16 DST=188.8.131.52 LEN=483 TOS=0x00 PREC=0x00 TTL=255 ID=45518 PROTO=UDP SPT=5353 DPT=5353 LEN=463
Aug 10 230746 boxster hostapd wlan0 STA f81edfdee7fb IEEE 802.11 disassociated
I've tried power off, reseating card etc. There are (many) other reports of this type of failure from earlier kernels. This one is for 2.6.38
I can supply more information if you need it. The failure does not seem to be related to any particular data flow or usage scenario (or load).
thanks very much for your assistance.