Wierd problem with Nokia Siemens SL2-141


I am facing a very wierd problem with Nokia Siemens SL2-141 wireless modem.
I got it from BSNL 2 weeks back (previously I was using Utstarocom router...I never faced such problem with it)...

Many a times, when I switch on my laptop, it fails to connect to the new router using WIFI. I have observed that this problem specially
occurs whenever I switch my router Off first and later on shutdown my computer.
On turning the laptop on later, wifi connection is not detected. So I have to use the network troubleshooter (I use windows 7), which
resets my network adapter and prompts me to switch off the router for atleast 10 seconds. This usually works, but sometimes it doesnt.
The strange thing is that whenever I face this problem, I am usually able to connect to the router using LAN successfully.

It seems as if the router is not broadcasting wifi signals whenever I have this problem because I am unable to connect to it
wirelessly using my another laptop or wifi enabled mobile.

I have already updated the drivers to the latest. And the router is set to run with DHCP enabled.

Please help..