Wireless problems with Atheros AR9285

I have a Samsung N210 and just installed Ubuntu. I'm new to Linux and I have some problems.

I'm using Linksys WRT110 Router. When I'm connected via ethernet cable everything's fine but when I unplug the cable and try to use wireless it's really problematic. The connection is unstable. I can use the internet for 5 minutes and then for a couple minutes it's gone and it comes back again and so on. But the thing is, it always shows that it's connected, but I can't connect to any websites. As I said, no problems with ethernet cable.

I made some research, installed Samsung-tools (and then came here to ask) and Realtek 8192E wireless driver for the latest kernel for Samsung netbooks with no luck. Also I uninstalled Network Manager and installed wicd, that didn't work either. What may be the problem?

Here is the output of the lspci command:

00:00.0 Host bridge: Intel Corporation N10 Family DMI Bridge
00:02.0 VGA compatible controller: Intel Corporation N10 Family Integrated Graphics Controller
00:02.1 Display controller: Intel Corporation N10 Family Integrated Graphics Controller
00:1b.0 Audio device: Intel Corporation N10/ICH 7 Family High Definition Audio Controller (rev 02)
00:1c.0 PCI bridge: Intel Corporation N10/ICH 7 Family PCI Express Port 1 (rev 02)
00:1c.1 PCI bridge: Intel Corporation N10/ICH 7 Family PCI Express Port 2 (rev 02)
00:1c.2 PCI bridge: Intel Corporation N10/ICH 7 Family PCI Express Port 3 (rev 02)
00:1c.3 PCI bridge: Intel Corporation N10/ICH 7 Family PCI Express Port 4 (rev 02)
00:1d.0 USB Controller: Intel Corporation N10/ICH 7 Family USB UHCI Controller #1 (rev 02)
00:1d.1 USB Controller: Intel Corporation N10/ICH 7 Family USB UHCI Controller #2 (rev 02)
00:1d.2 USB Controller: Intel Corporation N10/ICH 7 Family USB UHCI Controller #3 (rev 02)
00:1d.3 USB Controller: Intel Corporation N10/ICH 7 Family USB UHCI Controller #4 (rev 02)
00:1d.7 USB Controller: Intel Corporation N10/ICH 7 Family USB2 EHCI Controller (rev 02)
00:1e.0 PCI bridge: Intel Corporation 82801 Mobile PCI Bridge (rev e2)
00:1f.0 ISA bridge: Intel Corporation NM10 Family LPC Controller (rev 02)
00:1f.2 SATA controller: Intel Corporation N10/ICH7 Family SATA AHCI Controller (rev 02)
00:1f.3 SMBus: Intel Corporation N10/ICH 7 Family SMBus Controller (rev 02)
05:00.0 Network controller: Atheros Communications Inc. AR9285 Wireless Network Adapter (PCI-Express) (rev 01)
09:00.0 Ethernet controller Marvell Technology Group Ltd. 88E8040 PCI-E Fast Ethernet Controller

Thanks in advance for all the suggestions.

P.S.: When I open System > About Ubuntu, it says "You are using Ubuntu 11.04 - the Natty Narwhal - released in April 2011 and supported until October 2012." Why does it say 11.04? And April 2011, huh?