I know this thread is old but I keep running into it. I have fixed it 2x now. It has to do with the .NK2 file.
C:/Documents and Settings/username/Application Data/Microsoft/Outlook/
First, Recreate the NK2 file. With Outlook closed, search for *.NK2 and rename the file. When Outlook opens, a new one should be created. Sometimes Outlook is closed but it is still running in the background. Make sure the process Outlook.exe is not running.
If this doesn't work, move the original .NK2 file out of the folder. Rename the .NK2 file that was newly created from the above steps. Stop Outlook and make sure Outlook isn't running in the background (Outlook.exe). Restart outlook then close it again. A new .NK2 file should have been be created. Rename it to something else. Move the original .NK2 file back into the proper folder and name it the original name (Outlook.NK2). The autofill should return once Outlook has been restarted.
I really don't know why this happens but it seems to happen to the same users over and over.
EDIT: This fixes the NO autofill problem. It doesn't seem to help the Autofill List issue. I misread the Thread title...apologies.
Edited by rundav, 21 May 2009 - 09:45 AM.