Wallace Houston, Instead of " AND isnull(p.TrackingNumber,'') <> '' "

I would sugguest to use

AND p.TrackingNumber=p.TrackingNumber

this code will ignore all NULL values and also works for all datatypes.

It looks like some of your queries are scanning complete table than using indexes, validate your code Vs existing indexes.

You can use query to know number of open connection for the month Jan 2007 for your typical case.

SELECT hostname, uid=rtrim(loginame), Program_name=rtrim(Program_name), dbname=db_name(dbid), status=rtrim(status)

FROM master.dbo.sysprocesses

where Program_name =...

If you are unable to trace back your code and fix the problem.  Try with different connection string for each month and also add "Application Name" in the connection string and...