The light blink only when in sleep mode. 
I think u off the sleep mode dy! try to enable back the sleep mode, wait till the phone sleep to save battery and the blue light will start to blink once it goes to sleep mode!
Or another way to make it blink is to have a active bluetooth connection, try to transfer a file over bluetooth it should blink!

FYI the light is not network light, its a bluetooth and sleep mode indication light!

If KO already no worry, change very cheap only, maybe rm10, max should be rm30, just that tiny led only la i'm not surprise if its only rm5, no need worry but be careful coz this is new model people then to cheap u ! Find these fella fix, he offer reasonable price    can ask price b4 u want fix!
http://forum.lowyat.net/topic/397229

U sure u waited for the phone to sleep? waited 30 min? coz i know it takes quite a bit of time b4 the phone sleeps!

wa can get rm10 housing for n73 meh?
everywhere i go ask also rm30 
If there block the light easy la, poke a hole,use lighter to heat up a metal a ball ben point should do it,then poke when the ball point is hot, then use a tin sheet of plastic transparent one and stick on the back of the cover to keep the dust from going inside. there blinking led again