Touch screen stopped working after recent updates

[Marcelo Magno T. Sales]

Hello,

I was out for a month and when I got back there was a long list of updates 
available. After updating the system (Kubuntu 14.04 LTS) and rebooting, my 
touchscreen stopped working. It was working perfectly before, and has always 
worked without requiring manual interventions from me since I bought this 
computer 2 years ago.
Any hints on how to debug this?

Thanks,

Marcelo