Since my last posting here, I have rebuilt my server using Ubuntu 8.04 LTS. I had completely forgotten about the quota patch I had applied from this thread earlier.
I soon noticed that my daily Quota reports did not seem to be changing and in particular, new users were not showing up in the reports. I checked and the maildirsize files are not be created.
So I applied the patch to the new server and sent some test emails. Again, the maildirsize files were not created. I then created a blank maildirsize file and sent emails to see if the file would be updated. It was not.
So it appears that the patch works in the 7.10 version of Ubuntu, but not the 8.04.