I strumbled on this bug lately:

If a reference field with the autocomplete widget enabled is set as required, it gives a "ReadyState: 0" error in a dialog window. If it's set unrequired, the error does not appear.

I have no knowledge at all about Ajax, but I suppose this should not happen normally.

Comments

Version:7.x-2.0» 7.x-2.x-dev
Priority:Major» Minor
Status:Active» Postponed (maintainer needs more info)

I can't replicate this under Ubuntu 12.10 with Chrome and latest dev. Please provide more details (e.g. browser/OS versions)

Thanks.

I am getting the same error

An AJAX HTTP request terminated abnormally.
Debugging information follows.
Path: http://mysite.com/taxonomy/autocomplete/field_tag
ResponseText:
ReadyState: 4

Works fine in Firefox.
Not working in Chrome.

Also, it doesn't work when creating the document. It works fine when editing a document.

I am getting the same error

An AJAX HTTP request terminated abnormally.
Debugging information follows.
Path: http://mysite.com/taxonomy/autocomplete/field_tag
ResponseText:
ReadyState: 4

Works fine in Firefox.
Not working in Chrome.

Also, it doesn't work when creating the document. It works fine when editing a document.

Also, this began after I updated Drupal Core last week.