The steps are numbered and in order.
If any step fails, STOP there and we'll sort out the issue. Do NOT proceed to later steps and please do NOT try things. That approach will reduce confusion for both of us.
Each line command I've listed can be selected in Firefox with your mouse, copied with right-click, and pasted into the terminal window with right-click. Please do each command one at a time.
Step 0.
You've already flashed your liquid smooth rom to your phone and you already have a live usb of Ubuntu 12.04 LTS that's worked.
Step 1.
Get your boot.img file from your rom zip. In Windows, make a zip of it (right click on it in your File Explorer), and then Gmail it to yourself.
The point is to get the boot.img to where you can find it once you're in Linux in the easiest possible way.
Step 2.
Boot into Linux, get a terminal window with alt-control-t and open Firefox.
Step 3.
In the terminal window:
cd Downloads
rm *
rm -rf *
Step 4, verify.
In terminal window:
ll
(That's two small L's) You should not see any files.
Step 5.
In Firefox, goto your Gmail and choose to download boot.img.zip
Step 6.
In Firefox, choose to download fastboot.zip from this thread.
Step 7.
In terminal window (you're still in Downloads, you haven't changed anything since Step 3):
unzip *.zip
Step 8, verify.
ll
You should see listings for boot.img.zip, fastboot.zip, fastboot-linux and boot.img.
Stop and report if you don't see those.
Step 9.
In terminal window -
chmod 755 fastboot-linux
Step 10.
In terminal window -
sudo ./fastboot-linux devices
Stop and report exactly what the terminal window shows if you don't get your device.
Step 11, only if you saw your device listed in step 10 -
sudo ./fastboot-linux flash boot boot.img