problem with date range search using acts as solr

Hi,
i am struck up with solr's date range search.
I have used acts_as_solr plugin in my rails project. My model looks like

acts_as_solr :fields => [:title,{:createdate=>:date}]

No problem,if i used following date range search format
         => model.find_by_solr("createdate:[NOW-1DAY TO NOW+1DAY"]

if i used following format
         => model.find_by_solr("createdate:[2010-07-02T00:00:00.000Z TO
2010-08-02T00:00:00.000Z]")
i got error like
       "RuntimeError: There was a problem executing your search:
       Couldn't connect to the Solr server at
http://127.0.0.1:8982/solr. 400
       'Invalid_Date_in_Date_Math_String20100702T00_t00_t00000Z'",

how to resolve this problem ?