Linksys Cable / DSL :: WAG120N Yellow Sign On Icon Saying No Network Access

It has been 4 months my Router " Wag 120n ". The Router Gives Me A yellow Sign on the network Icon Sying " No network Access "  and the wireless Led is blinking with 1 sec interval  So

- I cant open Router's Home Page
- there is No ping to 192.168.1.1 " General Failure or Host unreachable " response 
- The Only way to get connected again is to replug the router from electricity , it works normally for 5 min and the Yellow Sign shows up again 
 
the Solutions I Tried to fix that up :-

1) Hard reset the 30/30/15 reset
 2) Firmware re-flashing 
 3) Trying an old firmware 1.0.0.12 instead of 1.0.0.16

but nothing of those worked the Only thing that worked for like 20 min the firmware upgrade  but after that the problem came up again the problem happens to all Computers on the network wired or on wireless happens on all kind of operations systems win7, xp, vista, (Android for mobiles).