I have a problem with a sales report I created.  It asks for a start date and end date for the records to be included.  If I choose 1/1/2013 to 1/31/2013, the report takes about 30 seconds to run.  If I choose 1/1/2013 to 2/28/2013 the report takes about 40 seconds to run.  But if I choose 2/1/2013 to 2/28/2013 it never finishes.  The closer my start date gets to 2/1, the longer the report takes to run! So if start date is 1/27, report takes 1 1/2 minutes, 1/29 - 3 minutes  1/31 - no finish.  Anyone ever run across this kind of problem?

Database is MS SQL 2008.  Going over RDC.  The tables are not that large. The main table is only 11000 rows, but the selection formula brings it down to less than 500 rows per month. The linked table is not indexed & has over 900,000 rows.   But what has me puzzled is that if I run the report from 1/1/13 to 2/28/13 it takes only a minute to run.  But if I run it from 2/1/13 to 2/28/13 (a shorter period with less records), it never finishes.  And it seems that the closer my start date gets to 2/1, the longer it runs, which I find counter-intuitive.  And if the problem were in a record from the 2/1 to 2/28 period, why will the 1/1 to 2/28 report run fine, and in a short time?
  

I ran it in SMS yesterday.  I found what's causing the problem, and was able to fix it.  I'm not sure why it worked previously & didn't on the later dates!  I was linking my order header table, which had order #, sales rep, date to a detail table that had all the lines for the order with a inner join.  I was also linking my user name table to the order header table by sales rep  with a left outer join.  I changed the link  from the order header table to the order detail table to pull the user name and now it works fine.
Thanks for the help