Wireless network don't work in ad-hoc mode with Atheros AR5212 since kernel 2.6.15-27-386

The kernel 2.6.15-27-386 is the last kernel that ad-hoc mode worked with Atheros AR5212.

Check this out:

In kernel 2.6.15-27-386:

marco@purusha:~$ lspci
[...]
00:0b.0 Ethernet controller: Atheros Communications, Inc. AR5212 802.11abg NIC (rev 01)
[...]

marco@purusha:~$ iwconfig
ath0 IEEE 802.11g ESSID:"MarcoSara"
          Mode:Ad-Hoc Frequency:2.422 GHz Cell: 02:13:46:94:20:9D
          Bit Rate:0 kb/s Tx-Power:18 dBm Sensitivity=0/3
          Retry:off RTS thr:off Fragment thr:off
          Power Management:off
          Link Quality=69/94 Signal level=-26 dBm Noise level=-95 dBm
          Rx invalid nwid:13 Rx invalid crypt:0 Rx invalid frag:0
          Tx excessive retries:176 Invalid misc:176 Missed beacon:0

Just work Fine!
But in after kernels don't. I Have tested with all past kernels including the kernel 2.6.20-16-generic, no success.

Check this out in kernel 2.6.20-16-generic, but others have same results:

marco@purusha:~$ iwconfig
ath0 IEEE 802.11g ESSID:"MarcoSara" Nickname:""
          Mode:Managed Frequency:2.437 GHz Access Point: Not-Associated
          Bit Rate:0 kb/s Tx-Power:18 dBm Sensitivity=0/3
          Retry:off RTS thr:off Fragment thr:off
          Power Management:off
          Link Quality=0/94 Signal level=-96 dBm Noise level=-96 dBm
          Rx invalid nwid:0 Rx invalid crypt:0 Rx invalid frag:0
          Tx excessive retries:0 Invalid misc:0 Missed beacon:0

Only mode acepted is "Managed", see:

marco@purusha:~$ sudo iwconfig ath0 mode ad-hoc
Password:
Error for wireless request "Set Mode" (8B06) :
    SET failed on device ath0 ; Invalid argument.

root@purusha:~# iwconfig ath0 mode Master
Error for wireless request "Set Mode" (8B06) :
    SET failed on device ath0 ; Invalid argument.

root@purusha:~# iwconfig ath0 mode Repeater
Error for wireless request "Set Mode" (8B06) :
    SET failed on device ath0 ; Invalid argument.

root@purusha:~# iwconfig ath0 mode Secondary
Error for wireless request "Set Mode" (8B06) :
    SET failed on device ath0 ; Invalid argument.

root@purusha:~# iwconfig ath0 mode Monitor
Error for wireless request "Set Mode" (8B06) :
    SET failed on device ath0 ; Invalid argument.

root@purusha:~# iwconfig ath0 mode Auto
Error for wireless request "Set Mode" (8B06) :
    SET failed on device ath0 ; Invalid argument.

Including the AUTO mode is disabled. I don't Know what to do. Check my modules loaded:

root@purusha:~# lsmod
Module Size Used by
binfmt_misc 11272 1
rfcomm 37660 0
l2cap 22276 5 rfcomm
bluetooth 51300 4 rfcomm,l2cap
nfsd 214384 13
exportfs 5632 1 nfsd
lockd 63112 2 nfsd
sunrpc 155452 8 nfsd,lockd
ppdev 9220 0
speedstep_lib 5124 0
cpufreq_userspace 4116 0
cpufreq_stats 5508 0
cpufreq_powersave 1792 0
cpufreq_ondemand 7676 0
freq_table 4740 2 cpufreq_stats,cpufreq_ondemand
cpufreq_conservative 6560 0
tc1100_wmi 7172 0
pcc_acpi 12160 0
dev_acpi 11140 0
sony_acpi 5388 0
video 15492 0
sbs 14752 0
i2c_ec 4992 1 sbs
dock 9216 0
button 7696 0
battery 9860 0
container 4352 0
ac 5124 0
asus_acpi 16412 0
backlight 6016 1 asus_acpi
xt_tcpudp 3328 2
ipt_MASQUERADE 3456 1
iptable_nat 7684 1
nf_nat 17964 2 ipt_MASQUERADE,iptable_nat
nf_conntrack_ipv4 17932 2 iptable_nat
nf_conntrack 59864 4 ipt_MASQUERADE,iptable_nat,nf_nat,nf_conntrack_ipv4
nfnetlink 6680 3 nf_nat,nf_conntrack_ipv4,nf_conntrack
ip_tables 12232 1 iptable_nat
x_tables 15108 4 xt_tcpudp,ipt_MASQUERADE,iptable_nat,ip_tables
ipv6 252512 14
lp 11332 0
wlan_wep 7040 1
snd_intel8x0 32796 1
snd_ac97_codec 97184 1 snd_intel8x0
ac97_bus 2304 1 snd_ac97_codec
snd_pcm_oss 43264 0
snd_mixer_oss 16512 1 snd_pcm_oss
wlan_scan_sta 13696 1
snd_pcm 76680 3 snd_intel8x0,snd_ac97_codec,snd_pcm_oss
ath_rate_sample 13184 1
snd_seq_dummy 3844 0
snd_seq_oss 31616 0
snd_seq_midi 8576 0
snd_rawmidi 24448 1 snd_seq_midi
snd_seq_midi_event 7424 2 snd_seq_oss,snd_seq_midi
ath_pci 95392 0
psmouse 37640 0
snd_seq 49648 6 snd_seq_dummy,snd_seq_oss,snd_seq_midi,snd_seq_midi_event
snd_timer 22276 2 snd_pcm,snd_seq
snd_seq_device 8204 5
snd_seq_dummy,snd_seq_oss,snd_seq_midi,snd_rawmidi,snd_seq
serio_raw 6916 0
xpad 8964 0
parport_pc 34980 1
parport 35272 3 ppdev,lp,parport_pc
pcspkr 3072 0
rtc 13104 0
snd 51716 12 snd_intel8x0,snd_ac97_codec,snd_pcm_oss,snd_mixer_oss,snd_pcm,snd_seq_oss,snd_r$
soundcore 7520 1 snd
snd_page_alloc 9992 2 snd_intel8x0,snd_pcm
wlan 203076 5 wlan_wep,wlan_scan_sta,ath_rate_sample,ath_pci
ath_hal 191696 3 ath_rate_sample,ath_pci
sis_agp 8708 1
agpgart 34096 1 sis_agp
i2c_sis96x 5508 0
i2c_core 21776 2 i2c_ec,i2c_sis96x
shpchp 33300 0
pci_hotplug 31160 1 shpchp
af_packet 20872 4
tsdev 7872 0
evdev 10112 4
joydev 9920 0
usbhid 25056 0
hid 25728 1 usbhid
ext3 129288 1
jbd 53032 1 ext3
mbcache 8196 1 ext3
ide_cd 31648 0
cdrom 36512 1 ide_cd
ide_disk 16000 3
pata_sis 13324 0
ata_generic 8196 0
libata 125208 2 pata_sis,ata_generic
scsi_mod 141580 1 libata
sis5513 13832 0 [permanent]
floppy 58020 0
sis900 23296 0
mii 5632 1 sis900
generic 4228 0 [permanent]
ehci_hcd 32780 0
ohci_hcd 21252 0
usbcore 131480 5 xpad,usbhid,ehci_hcd,ohci_hcd
raid10 24704 0
raid456 123408 0
xor 15752 1 raid456
raid1 23936 0
raid0 8704 0
multipath 8832 0
linear 6400 0
md_mod 77076 7 raid10,raid456,raid1,raid0,multipath,linear
thermal 13832 0
processor 22956 1 thermal
fan 4740 0
dm_mod 57164 4
fbcon 41760 0
tileblit 2688 1 fbcon
softcursor 2304 1 bitblit
vesafb 8196 0
capability 5000 0
commoncap 7296 1 capability

This list of modules are the list in a kernel that wireless in ad-hoc mode doesn't work. But in Kernel kernel 2.6.15-27-386 that works the modules
wlan 203076 5 wlan_wep,wlan_scan_sta,ath_rate_sample,ath_pci
ath_hal 191696 3 ath_rate_sample,ath_pci
wlan_scan_sta 13696 1

Are loaded too!

My /etc/network/interfaces:
auto ath0
iface ath0 inet static
address 192.168.0.1
netmask 255.255.255.0
wireless-essid MarcoSara
wireless-mode ad-hoc
wireless-channel 9
wireless-key AA00BB11CC

Do you know how to fix it ? Thanks!