A patch for Crackdown should download automatically the next time you run the game while you're hooked up to Xbox Live, if it hasn't already.
The patch takes care of "several minor technical issues" that contribute to a "smoother online gameplay experience", so let us know how you get on with that.
You should also notice a larger number of gang vehicles dotted around the city, which Major Nelson reckons will help with the Repo Man achievement. It's the one about taking over 100 gang cars, obviously.
Of course, this patch isn't to be confused with the forthcoming downloadable content, a few details of which YOU managed to claw out of producer Phil Wislon in last week's Crackdown Community Q&A. Apparently we can expect more news on the official DLC line-up soon.