Problem with my Wifi network

Hi,

I have problem with my wifi network. I have laptop Studio 1749,  purchased before 18 months. Everything was fine, but 3 days ago I started having problem with connection to my Wifi. It's constantly disconecting me, sometimes it connects  itself immediately, sometimes I have to connect it and sometimes an error message appears, that Windows can't connect my Wifi and only solution of this error message is restarting of Wireless Network Adapter.

I have Win 7. My Wireless Network Adapter is DW1520 Wireless-N WLAN half-mini card and router is Linksys WRT120N. Security Mode of the router is WPA2 Personal and Encryption is "TKIP or AES".

I have already tried this:
   Upgrade drivers of DW 1520
   Upgrade firmware of the router
   Change channel of the router
   Change network Mode of WRT120N from BGN to BG.
   Unchecked "allow the computer to turn off this device to save power" under power management
   Also disabled bluetooth adapter.

TCP/IPv4 and TCP/IPv6 are same as PudgyOnes.

The power of wireless signal is excelent.

I have also connected to the same Wifi network computer, where's everything fine, without any problems...

Could somebody help me, please?