How do I record a computer monitor without banding/flickering with a Canon t2i/550D?
While reviewing the Instruction Manual for the Canon 2Ti EOS 550 on page 127 you will find information on how to manually set the shutter time. Here is the pdf download for the manual:
http://gdlp01.c-wss.com/gds/9/0300003169/01/eosrt2i-eos550d-im-en.pdf

There is wide range of 1/4000 to 1/30 of a second to work with depending on your frame rate.

For 50 fps or 60 fps the range is 1/4000 to 1/60.

For 24, 25, &amp; 30 fps the range is 1/4000 to 1/30.

I suggest that you try different shutter times at your preferred frame rate. I know this is not definitive, as I don't have this camera, nor have I tested this. However, the flicker you are referring to is as you suggest a synchronization issue; you are trying to have the camera capture at a rate that synchronizes with the display. Another thing you can try is change the display frame rate, if you have this option on your monitor.

Hope this helps,