Maybe there was some component loosely connected and the added vibration of the cat jumping on the computer caused those connection to fail.
The bad video may be caused by the video card been slightly out of it's connector.
Unplug the computer, open the case and check to make sure that ALL components are securely connected. (keep the cat away during that time :) )
Remove and replace all cards and memory sticks in the same locations.
Take the oportunity to dust it of.
Electro
May 2011