It happens to us all the time on 1.1.6 so we use a different Rails adapter for MySQL
Follow the directions here and see if that helps. I understand they tickered with the ruby-only mysql adapter in 1.2 so this might still be a better option:
I thought the problem was still occurring even after [5637], but it
turns out we had vendor/rails frozen to the 1.2 tag instead of the 1.2
branch, so we didn't have the fix. It seems to be working fine now.