Arduino video adapter?

I have a time sensetive routine that can't be interrupted for more than a millisecond or so. I found that updating the 16*2 LCD one full line took about 4.2 milliseconds and I need to update two lines so around 8ms. I have this crazy idea to make an arduino video adapter out of my spare atmega168. I think if I use another atmega to run the video update and my problem could be solved. Chattig between two arduinos should be quick, right? (But how?) Has anyone done a project with two atmega talking to each other? Any suggestions from the forum? Thanks.

At least one project using I2C to communicate between 2 Arduinos has been posted in "Exhibition", and I'm pretty sure that there's been one using the "slave" Arduino as an LCD controller.