Well, I had same problem after I installed an update of 140 MB.
Then, I downloaded an update from ASUS website for the phone, of around 1.6 GB.
I copied the update zip file to memory card.
Inserted it in the phone, and went to Recovery Mode (By pressing Vol. Down + Power, till ASUS logo appears)
There, I selected 'Install Update From External Storage', and chose the update zip file. And Waited like 10 minutes. And Boom! The phone started working.
I hope, this works for you too.