Firmware version 1.0.9 is available from the Canon website. This latest firmware update fixes a tonal jump issue when using the auto lighting optimiser settings.

To check the current firmware version of the Canon EOS 550D you need to set the mode dial to the “P” setting then press the Menu button. Navigate along to the third spanner button and the current firmware version will be displayed at the bottom of the list, in my case it was version 1.0.8.

Warning: Sometimes, firmware updates can go wrong which could render equipment unusable so ensure you really need the update before you  apply it and make sure you have thoroughly read the instructions before applying any firmware updates.

Download, and instructions, for firmware version 1.0.9 for the Canon EOS 550D can be found at Canon: EOS Rebel T2i / 550D Firmware Update Version 1.0.9.