WPA authentication - regression on 12.04 / ath9k

Since I upgraded my desktop to 12.04, I have observed a bad regression w.r.t. my WiFi access. Everything else the same, I used to be very happy with my USB-dongle TP-Link TL-WN721N (Atheros AR9271). I was connected always, immediately, and reliably for days on a go.
After the upgrade, it connects only once out of 3, and asks repeatedly for the WiFi key, over and over. Even when entering the correct one, it will not connect and ask again ... .

To debug, I have released the strict WPA2, AES only on the access point to any WPA*. The same thing can be observed, still, under these relaxed conditions:
Bit Rates:1 Mb/s; 2 Mb/s; 5.5 Mb/s; 6 Mb/s; 9 Mb/s
                              11 Mb/s; 12 Mb/s; 18 Mb/s
                    Bit Rates:24 Mb/s; 36 Mb/s; 48 Mb/s; 54 Mb/s
                    Mode:Master
                    Extra:tsf=00000000ca0b7181
                    Extra: Last beacon: 25856ms ago
                    IE: Unknown: 00057769726173
                    IE: Unknown: 010882848B0C12961824
                    IE: Unknown: 030108
                    IE: IEEE 802.11i/WPA2 Version 1
                        Group Cipher : TKIP
                        Pairwise Ciphers (2) : CCMP TKIP
                        Authentication Suites (1) : PSK
                    IE: WPA Version 1
                        Group Cipher : TKIP
                        Pairwise Ciphers (2) : CCMP TKIP
                        Authentication Suites (1) : PSK
                    IE: Unknown: 2A0100
                    IE: Unknown: 32043048606C

In order to provide clear information, I have switched between a dongle TP-Link TL-WN321G and the one mentioned above; just by plugging in and out; not touching anything else.

I attach the syslog, showing how quickly the tr73usb connects after I removed the ath9k from the previous swap of the dongles From 19:40:44 it takes around 7 seconds to authenticate.
Then I remove this dongle and plug back the one with ath9k. The syslog clearly shows that it takes close to one minute, until after a good handful number of trials, to get it connected. I repeat: in most cases it doesn't. My grouses are not on the long time, but that it usually times out before a trial becomes successful.

I don't say this is a strong signal:
Mode:Managed Frequency:2.447 GHz Access Point: 00:11:F5:22:24:40
          Bit Rate=11 Mb/s Tx-Power=20 dBm
          Retry long limit:7 RTS thr:off Fragment thr:off
          Power Management:off
          Link Quality=37/70 Signal level=-73 dBm
          Rx invalid nwid:0 Rx invalid crypt:0 Rx invalid frag:0
          Tx excessive retries:0 Invalid misc:559 Missed beacon:0
, but too strong to blame it. Especially since the said rt73usb and an even older zd1211 (3Com) connect favourably.

ProblemType: Bug
DistroRelease: Ubuntu 12.04
Package: wpasupplicant 0.7.3-6ubuntu2
ProcVersionSignature: Ubuntu 3.2.0-26.41-generic 3.2.19
Uname: Linux 3.2.0-26-generic x86_64
NonfreeKernelModules: fglrx
ApportVersion: 2.0.1-0ubuntu8
Architecture: amd64
Date: Fri Jul 13 20:05:08 2012
InstallationMedia: Kubuntu 10.04 LTS "Lucid Lynx" - Release amd64 (20100427)
ProcEnviron:
 LANGUAGE=
 TERM=xterm
 LANG=en_US.UTF-8
 SHELL=/bin/bash
SourcePackage: wpasupplicant
UpgradeStatus: Upgraded to precise on 2012-06-14 (29 days ago)