[horde] Address AutoComplete for Imp Compose Not Working, Horde Groupware Webmail Edition 5.2.2, Imp 6.2.2, Turba 4.2.2

[Andy Dorman]

I am sure I have done something really dumb to disable address 
auto-complete in Imp's compose window, but I can not figure out what I 
have set to cause it to stop working.

Earlier this year address auto-complete worked fine, but this is a beta 
test install.  So we have been experimenting and testing along with 
upgrading and at some point (not exactly sure when) auto-complete 
stopped working.

Our turba backends.local.php file disables the localsql address book and 
sets up the personal_ldap address book and everything works great except 
auto-complete when composing an email.

Here is what happens (or more correctly doesn't happen):

The imp compose window opens, I enable firebug to monitor what is going 
on and start typing a To|CC|BCC address.  When I get to the third char 
($conf['compose']['ac_threshold'] = 3;) nothing happens.  There is 
nothing in the firebug console log and no net traffic.

It is as if there are no js actions attached to the address fields in 
the compose window at all.

So I expect I have set something somewhere in our beta test imp or turba 
configs, prefs or backend settings that has disabled address 
auto-complete so that it is not even loaded into the compose 
window....but I have searched the docs and the files and have found 
nothing that looks like it could turn off address auto-complete.

One last bit of information, our production webmail installation (very 
old version using the basic interface) uses the same personal_ldap 
address book and settings and address auto-complete works fine there as 
well.

So does anyone know which innocent-looking imp|turba config, backend, or 
pref setting that could completely disable address auto-complete in the 
imp compose window?

Thanks in advance for helping me find my silly mistake.

-- 
Andy Dorman