I'm on a 2011 Lenovo Thinkpad T420i with a Realtek RTL8188CE WiFi adapter. Here's the scenario:

1. I pop in the Ubuntu LiveCD to install. Laptop detects all networks in range, I connect to my home network, internet working great.
2. Once Ubuntu finishes installing, the home network I am connected to is the only one which appears in the applet list.
3. Upon restarting or waking from suspend, NetworkManager does not detect any networks – it simply displays "Disconnected" under the Wireless Network section of the menu.

I am able to connect to my home network by using the "Connect to Hidden Wireless Network" option and it works immediately. I have yet to test if this works with other SSIDs. I have tried reinstalling the entire OS as well as NetworkManager and my wireless drivers.

For hardware info, I ran:

cormac@cormac-T420:~$ sudo lshw -c network

Here is the output for my wireless card:

*-network
description: Wireless interface
product: RTL8188CE 802.11b/g/n WiFi Adapter
vendor: Realtek Semiconductor Co., Ltd.
physical id: 0
bus info: pci@0000:03:00.0
logical name: wlan0
version: 01
serial: d0:df:9a:08:73:50
width: 64 bits
clock: 33MHz
capabilities: pm msi pciexpress bus_master cap_list ethernet physical wireless
configuration: broadcast=yes driver=rtl8192ce driverversion=3.2.0-26-generic firmware=N/A ip=192.168.1.138 latency=0 link=yes multicast=yes wireless=IEEE 802.11bgn
resources: irq:17 ioport:5000(size=256) memory:f2500000-f2503fff

I can provide more information if required. This was not a problem in Natty or Oneiric. I hope this can be fixed, I don't want to have to ask for an SSID wherever I need to connect.