My Wi-Fi stops working occasionally ,usually when downloading lots of data such
as when viewing a video.
The only way to get it back up is to Re-Boot
I have an Acer Aspire 1551-3671 with Ubuntu 12.04 (Precise Pangolin)



Here is some data on the problem
Note that phy0 is Hard Blocked


george@george-Aspire-1551:~$ sudo rfkill list
0: phy0: Wireless LAN
Soft blocked: no
Hard blocked: yes
1: acer-wireless: Wireless LAN
Soft blocked: no
Hard blocked: no

george@george-Aspire-1551:~$ iwlist wlan0 scan
wlan0 Scan completed :
Cell 01 - Address: C0:83:0AF:79:E9
Channel:9
Frequency:2.452 GHz (Channel 9)
Quality=48/70 Signal level=-62 dBm
Encryption keyn
ESSID:"2WIRE263"
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=000000872e55e181
Extra: Last beacon: 19760ms ago
IE: Unknown: 00083257495245323633
IE: Unknown: 010882848B0C12961824
IE: Unknown: 030109
IE: Unknown: 0706434120010B1B
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

lspci -v
06:00.0 Network controller: Atheros Communications Inc. AR9287 Wireless Network Adapter (PCI-Express) (rev 01)
Subsystem: Foxconn International, Inc. Device e034
Flags: bus master, fast devsel, latency 0, IRQ 17
Memory at d0300000 (64-bit, non-prefetchable) [size=64K]
Capabilities: <access denied>
Kernel driver in use: ath9k
Kernel modules: ath9k

That's enough signal and a reasonably reliable driver. It could be your isp. Investigate when you lose it and see what you lose,

I would try changing the channel to 13 or something in case some dweeb is using the same channel as you.

Did you check if there is any packet loss. If you find any packet loss happening then its your ISP problem.
To check the packet loss, try to connect LAN cable and verify instead of checking from Wifi mode.

Thanks
Wall stickers

Finally found the trouble

Two modules were loading

Before sudo rfkill list
0: phy0: Wireless LAN
Soft blocked: no
Hard blocked: yes
1: acer-wireless: Wireless LAN
Soft blocked: no
Hard blocked: no

Had to edit ect\modprobe\blacklist.conf
Add acer_wmi

now ~$ rfkill list
0: phy0: Wireless LAN
Soft blocked: no
Hard blocked: no

This seems to fix it