[CentOS] Wireless Interface Does Not Connect Automatically At StartUp

I have recently installed CentOS 6 on a system with  a Realtek 8180L
wireless card. The wireless card is detected properly and uses the
rtl8180 driver. But it connects to our wireless network only after
logging to the Desktop Environment (GNOME) and using the Network
Manager Applet. In order to make the wireless card connect to the
network automatically at system start up, I edited the Connection
using the Network Manager Applet and checked "Connect Automatically"
and "Available to all users" options.  However, while booting the
system, the following error message is displayed when the wireless
network interface is brought up.

Device does not seem to be present, delaying initialization

But as soon as a user logs on to the Desktop, he can connect to the
network using the NM Applet.

I have also toggled between using DHCP and Static IP Address for the
the wireless card but it makes no difference. The SSID is not being
broadcast and the Wireless Access Point / Router uses WPA-PSK.

TIA,
-- 
Manish Kathuria