ath5k: can not connect; random system freeze

Hi!
I'm experiencing troubles with my Wifi.
@ home: WEP 128, link quality changes from 1 bar to 4 bars without any reason as the AP and the PC are in the same room with the same trafic.

@ University: WAP (2?), also has the problem of the link quality. After some usage Wifi disconnect and is no more able to reconnect. The dmesg becomes full of Call Trace (see below). I also experience system crash: nothing is responding anymore! If rhythmbox is playing, it keeps looping at the same sound. There's still output, but it is awful; ex: laaaaaaaaaa.... The only solution is pushing on the power button and waiting till the PC is shutted down.

I'm a bit confused with the following; lspci reports the chipset to be Atheros Communications Inc. AR242x 802.11abg Wireless PCI Express Adapter (rev 01)
However, looking at the logs I got:
Dec 3 12:49:38 portant kernel: [ 14.188845] ath5k phy0: Atheros AR5414 chip found (MAC: 0xa0, PHY: 0x61)

Therefore I open a new bug.

Useful information and similar problems can be found there:
[1] https://bugs.launchpad.net/ubuntu/+source/linux-backports-modules-2.6.27/+bug/275423
[2] http://madberry.org/2008/11/how-to-get-atheros-ar242x-to-work-on-810-intrepid-ibex/

Call Trace:

Dec 3 12:53:00 portant kernel: [ 222.596855] ------------[ cut here ]------------
Dec 3 12:53:00 portant kernel: [ 222.596863] WARNING: at /home/antoine/compat-wireless-2008-12-02/net/mac80211/main.c:227 ieee80211_hw_config+0xac/0xb0 [mac80211]()
Dec 3 12:53:00 portant kernel: [ 222.596866] Modules linked in: ipv6 nfs lockd nfs_acl sunrpc aes_x86_64 aes_generic af_packet radeon drm binfmt_misc ppdev acpi_cpufreq cpufreq_stats cpufreq_userspace cpufreq_powersave cpufreq_ondemand freq_table cpufreq_conservative pci_slot container wmi sbs sbshc iptable_filter ip_tables x_tables parport_pc lp parport joydev snd_hda_intel snd_pcm_oss snd_mixer_oss snd_pcm snd_seq_dummy snd_seq_oss snd_seq_midi pcspkr snd_rawmidi evdev psmouse snd_seq_midi_event serio_raw snd_seq snd_timer snd_seq_device snd soundcore snd_page_alloc i2c_piix4 i2c_core arc4 ecb crypto_blkcipher video output ath5k mac80211 led_class cfg80211 battery ac button shpchp pci_hotplug ext3 jbd mbcache sr_mod cdrom sd_mod crc_t10dif pata_atiixp 8139cp ata_generic sg usb_storage libusual ahci ohci_hcd 8139too mii pata_acpi ehci_hcd libata scsi_mod dock usbcore thermal processor fan fbcon tileblit font bitblit softcursor fuse
Dec 3 12:53:00 portant kernel: [ 222.596959] Pid: 3057, comm: phy0 Tainted: G W 2.6.27-10-generic #1
Dec 3 12:53:00 portant kernel: [ 222.596963]
Dec 3 12:53:00 portant kernel: [ 222.596963] Call Trace:
Dec 3 12:53:00 portant kernel: [ 222.596972] [<ffffffff8024e9b4>] warn_on_slowpath+0x64/0x90
Dec 3 12:53:00 portant kernel: [ 222.596977] [<ffffffff80471d95>] ? net_ratelimit+0x15/0x20
Dec 3 12:53:00 portant kernel: [ 222.596986] [<ffffffffa024a06f>] ? ath5k_hw_reset+0xecf/0x1150 [ath5k]
Dec 3 12:53:00 portant kernel: [ 222.596992] [<ffffffff803a793c>] ? __ratelimit+0x7c/0xf0
Dec 3 12:53:00 portant kernel: [ 222.596995] [<ffffffff80471d95>] ? net_ratelimit+0x15/0x20
Dec 3 12:53:00 portant kernel: [ 222.597015] [<ffffffffa024d0af>] ? ath5k_reset+0x4f/0x240 [ath5k]
Dec 3 12:53:00 portant kernel: [ 222.597028] [<ffffffffa020340c>] ieee80211_hw_config+0xac/0xb0 [mac80211]
Dec 3 12:53:00 portant kernel: [ 222.597042] [<ffffffffa0207fc2>] ieee80211_scan_work+0x142/0x1b0 [mac80211]
Dec 3 12:53:00 portant kernel: [ 222.597055] [<ffffffffa0207e80>] ? ieee80211_scan_work+0x0/0x1b0 [mac80211]
Dec 3 12:53:00 portant kernel: [ 222.597062] [<ffffffff80262802>] run_workqueue+0xc2/0x1a0
Dec 3 12:53:00 portant kernel: [ 222.597065] [<ffffffff80262b0f>] worker_thread+0xaf/0x130
Dec 3 12:53:00 portant kernel: [ 222.597070] [<ffffffff80267050>] ? autoremove_wake_function+0x0/0x40
Dec 3 12:53:00 portant kernel: [ 222.597073] [<ffffffff80262a60>] ? worker_thread+0x0/0x130
Dec 3 12:53:00 portant kernel: [ 222.597078] [<ffffffff80266c1e>] kthread+0x4e/0x90
Dec 3 12:53:00 portant kernel: [ 222.597081] [<ffffffff80213c99>] child_rip+0xa/0x11
Dec 3 12:53:00 portant kernel: [ 222.597084] [<ffffffff80266bd0>] ? kthread+0x0/0x90
Dec 3 12:53:00 portant kernel: [ 222.597088] [<ffffffff80213c8f>] ? child_rip+0x0/0x11
Dec 3 12:53:00 portant kernel: [ 222.597089]
Dec 3 12:53:00 portant kernel: [ 222.597091] ---[ end trace 92794ffd4e88ba3c ]---