Difference in query processing time

[Karl Geppert]

What might cause the following query to take about 20 seconds to run in 
c# code, but only 47ms to run in luke-all 0.9.2 on the same query and 
same index (but without the sort)?

Is there any easy thing I can do to bring it to this speed?
                      hits = ixs.Search( bq, new Sort( new SortField[] 
{ new SortField( "name" ), SortField.FIELD_SCORE }) );

where bq is +name:DODECYLANILINE -type:U