One thing I think you are missing is that you haven't got the latest driver. I don't believe it is yet included in the kernel you installed. I'll post my complete solution below in case others are looking for this.
I had been struggling with this issue for months. Here's what finally worked for me and seems to be working for others on 14.04:
Download the latest driver (you might have to install git first)
git clone http://github.com/lwfinger/rtlwifi_new.git
Change into the new directory you just created
cd rtlwifi_new
Compile and install the new driver
make
sudo make install
Edit the settings for the driver
echo "options rtl8723be fwlps=0 swlps=0" | sudo tee /etc/modprobe.d/rtl8723be.conf
It's probably a good idea to take a look at that file to make sure that worked. Some people say the "swlps=0" part of the command above is unnecessary. I'm not sure but it doesn't seem to be hurting anything.
Reboot.
The next time your system updates the kernel, you may have to do this part again:
cd rtlwifi_new
make
sudo make install
I'd be curious to hear if others have tried this on releases other than 14.04 with success.
Good luck!
sudo service network-manager restart
? It doesn't fix your problem but might be easier than rebooting in the meantime. – mchid Dec 26 '14 at 19:18