New software - old problem.
When my R6.5 Domino Web Access users attempt to perform a name search against the server’s Directory Catalog (located on the one and only Domino Server) the list of names goes blank and the search returns nothing.
For anyone who wants to try and reproduce this issue, here are the steps:
A user clicks on To: or CC: in a new Memo to bring up the “Select Addresses” dialog window.
In the Search drop down list, select the Directory Catalog (sorted last name first name if that means anything).
The user types a last name in the “Find” window and clicks on the search button.
At this point, the list of names disappears and the search does not return anything (accept a blank screen).
The names my users are searching for do exist in the Directory Catalog and we’ve tried searches using the last name, first name, both first and last, etc. Same blank result.
The issue occurs only with the Directory Catalog and does not occur if the user performs a search against his Contacts list or any of the Domino Directories also on the server (these Directories are listed in Directory Assistance).
There is a TechNote (1089956) which describes the exact same problem. However, there is no workaround or fix suggested. It merely states that this no longer occurs in iNotes R5.0.9
And that may be, but it is definitely still occurring in R6.0.x and R6.5 codestreams! 
Any help or workarounds would be appreciated.