Was the burning from the cutter or the bearing (or both)?
How mush material are you taking off each pass?
When routing you need to keep the cutter moving to avoid burning, but you don't want to move so fast that you cause tearout. You can up your speed and minimize tearout by taking repeated shallow cuts.
You may need to slow your cutter speed too, do you have a variable speed router? Also, if the bearing is wearing out or not properly lubricated, or the cutter is not sharp, this can cause burning.
One last tip, you might try putting tape on the sides where the bearing will follow, this can help prevent the wood itself from being burnt.
MIMForum staff member - Melbourne, Australia