wireless connection problem

Hi everyone,
I am new to linux. I have installed ubuntu and I am booting together with window. But I have a problem of wireless connection in ubuntu.
If I start booting using ubuntu no wireless networks become available. If I first open window and restart it and open ubuntu then only I can get internet connection.
I dont understand what's the reason behind it.
Thanks in advance

Buggy drivers, probably. Is your card a broadcom? They're notorious for not ever releasing any specs and insisting everyone use their buggy binary-only drivers.

So, more details please. What's your wireless card? What drivers are you using?

This is the information about my wireless.

Intel Corporation PRO/Wireless 3945ABG [Golan] Network Connection (rev 02)

Do u need some more information? and thanks for reply