Corinne, that's interesting, I just tested the auto complete feature for vendors in vendor maintenance, AP Invoice Entry, Purchase Order Entry.  I also checked I with customers in Customer Maintenance.  It worked everywhere I tested it.

Additionally, F2 still invokes the Advanced Lookup Engine (ALE) in each of the above instances.  However, if I typed in a partial vendor name without then selecting from the choices provided and then pressed F2, the ALE popped up but the list was empty.

I tested using the sample company ABC with version 2014 running service pack 1.  (5.10.0.1)

I noticed your indication that your troubles seem to be with screens whose names are followed by an *.  The * indicates that there is a customization on the form.  This could have an impact of functionality.  You or your reseller should review the customizations made to the forms/panels involved to get a better idea of the cause of your challenge.