From the official site of Burnout Paradise:
"We've found a solution to the frame rate issue affecting some Xbox 360 users with the recently released Bogart software update.
We aim to recall the affected update from all 360s by this Friday.
We'll replace this with a revised update containing a fix for the frame rate issue. This should be with you in around a week's time - by 2nd May.
We'll confirm solid dates as soon as we have them.
Apologies for the inconvenience...we'll keep you posted if anything changes."