Enterprise Manager

Hi,
I am getting "End of file on communication channel error" while we run some quries in our

DB but if we modify those quries then they run fine. Yesterday we added an order by clause

at the end of our query and it stopped running with "End of file on communication channel".

That query was running fine without that order by clause. I ran that same query in our stand

by db but got the same error with order by clause. A week ago i created test DB using export

import and that query was running fine there with order by clause.
Below is the query with order by clause.
------------------------------------------
SELECT ALL emp.EMP_ST||emp.OLD_EMP_CODE OLD_CODE, PAY_DESIG.DESG_DESC,

s_d_w,PAY_DEPT.DEPT_DESC,
emp.EMP_CODE,emp.SHFT_GROUP, emp.NAME,gross_pay,
to_number( decode(ltrim(rtrim(emp.GRAD_CODE)),'3A','3.5',NULL,0,ltrim(rtrim(emp.GRAD_CODE)))

)GRAD,
decode(ltrim(rtrim(emp.GRAD_CODE)),'0',null,emp.grad_code) grad_code
,emp.JOIN_DATE, PAY_COST.COST_DESC,
emp.DEPT_CODE,emp.COST_CODE
FROM emp, PAY_DESIG, PAY_DEPT, PAY_COST
WHERE emp.DEPT_CODE = PAY_DEPT.DEPT_CODE
AND emp.DESG_CODE = PAY_DESIG.DESG_CODE
AND PAY_COST.COST_CODE = emp.COST_CODE
--and emp.DEPT_CODE BETWEEN :DEPT1 AND :DEPT2
and emp_code in (select emp_code from pay_month_mst where

to_char(pay_date,'mm-yyyy')='09-2005')
--and quit_stat is null
and substr(emp_code,1,1) in (1,8)
and SSI_enttl='Y'
ORDER BY emp.emp_code
--------------------------------------------------
I then changed substr(emp_code,1,1) with "and (emp_code like '1%' or emp_code like '8%')"
After that change query start running without any Error.
Any Idea