We have recently upgraded a customer from version 4.03 to 2009 R2 and then in to 2013 and then into 2013 R2.
After conversation as shown in MSDN When we opening NAV 2013 R2 RTC it throws an error of unable server and in background SQL query for drop view of G\L entry is running.
And that process is never ending, we have to restart the SQL server service.