Got an apparent autocomplete problem at the IowaGeocachers.org site. The same problem appears there for both node-reference and user-reference auto completions.
In both cases I generally get an error pop-up like this:
http://iowageocachers.org/nodereference/autocomplete/field_favorite_earthcache
{ 'GC1005K [nid:12706]': '<div class='reference-autocomplete'>GC1005K</div>',
'GC100AV [nid:12707]': '<div class='reference-autocomplete'>GC100AV</div>',
'GC100CA [nid:12708]': '<div class='reference-autocomplete'>GC100CA</div>',
'GC100CR [nid:12709]': '<div class='reference-autocomplete'>GC100CR</div>',
'GC100G5 [nid:12710]': '<div class='reference-autocomplete'>GC100G5</div>',
'GC100GJ [nid:12700]': '<div class='reference-autocomplete'>GC100GJ</div>',
'GC100GQ [nid:12701]': '<div class='reference-autocomplete'>GC100GQ</div>',
'GC100Q1 [nid:12711]': '<div class='reference-autocomplete'>GC100Q1</div>',
'GC100VH [nid:12712]': '<div class='reference-autocomplete'>GC100VH</div>',
'GC100X1 [nid:12713]': '<div class='reference-autocomplete'>GC100X1</div>' }
<b>[phpBB Debug] PHP Notice</b>: in file <b>/includes/session.php</b> on line <b>1021</b>: <b>Cannot modify header information - headers already sent by (output started at /aaa/bbb/ccc/includes/common.inc:2497)</b><br />I also tried some very similar autocompletions in other sites running on the same server, using the very same codebase... and had NO problems.
I'm left wondering if I have exceeded some limit to the number of nodes (or users) that such a field can pull from? This site has more than 12700 (as you can see above) nodes that match this particular filter spec and we also have in excess of 12000 active user accounts to reference.
Update: In fact, I changed some of the offending fields from "autocomplete" to "select list" and found that the errors are gone. However, the site is using much more process memory in this configuration, in some instances. I believe this is because some of my CCK data types include multiple node reference data types and in the select list mode the forms that edit these selections have to display the entire list of 12000+ nodes many times over. So, I'm almost certain this is a memory/resource limit issue.
Some details: Drupal 6.17, Node Reference 6.x-2.7, User Reference 6.x-2.7
Anybody suggest how to debug this or where to look for an alternative means to entering these node and user references?
Thanks.