Default [Q] How can I fix a Security Error on LG Optimus Vu II - F200K?

Hi,

I have an Optimus Vu 2 (F200K), which I rooted via the universal 4.1.2 method found in the XDA Developers forums. After downloading an update, I experienced an error, after which the phone is stuck in a bootloop showing Security error. Please help me fix it. The specs of the Vu 2 are:

1. 1024*768 [4:3] 5" screen.
2. 2 GB RAM
3. 1.5 GHz Dual-Core Krait CPU
4. Adreno 225 GPU
5. Android 4.1.2 Jelly Bean

So, can anyone suggest a fix? Please reply quickly.

UPDATE:

After randomly pressing keys, I got this screen. What does it mean? The link to the image is: i40.tinypic.com/2je4qe1.jpg