collective.solr and search results ordering

I'm using collective.solr 3.1 with Plone 4.3.  The @@search form does not return results in alphabetical order (or at least not in an order I think is alphabetical) despite the URL indicating the index it is using:

SITEURL/@@search?SearchableText=jen&b_start:int=0&sort_on=sortable_title

Yet, the "Sort by date (newest first)" filtering does work correctly.

Has anyone else run into this?

	Kim


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