Symptoms
Running CHECKDB against a database with at least 122,000 objects, causes a stack overflow exception. The number of objects is represented by the count of rows in SYSOBJECTS, NOT the number of tables in the database.
The stack overflow exception may cause Microsoft SQL Server to shutdown. If it does the client will receive a message that the connection has been broken. If the exception does not shutdown Microsoft SQL Server, the client will appear to be still running the DBCC.

Resolution
Instead of using CHECKDB, use a script to run DBCC CHECKALLOC as well as a loop that executes DBCC CHECKTABLE for all system and user tables. Following is a script that performs this task, that can be scheduled and run using ISQL:

DBCC CHECKALLOCGOdeclare @tabname sysnamedeclare @exec_string varchar(300)declare tabcr cursor forselect name from sysobjects where type = ‘S’ or type = ‘U’ order by nameopen tabcrfetch tabcr into @tabnameselect @exec_string = “dbcc checktable(‘” + @tabname + “‘)”select @exec_string = rtrim(@exec_string)exec(@exec_string)while (@@fetch_status = 0)begin fetch tabcr into @tabname select @exec_string = “dbcc checktable(‘” + @tabname + “‘)” exec(@exec_string)endclose tabcrdeallocate tabcr