Service Entry Sheer

Dear Gurus....

I have created a Service PO with Acct.Assgnmt K and Item Category D and maintained the services in the services tab and saved...its working OK....

Now I must do the SES in ML81N....as soon as I load the PO number system issues a Message in GREEN saying "Customizing Incorrectly Maintained" BUT after I click on the Create New Entry Sheet Button message disappears and SES runs normally...and even the MIRO is OK....

Can someone tell why this message "Customizing Incorrectly Maintained" is throwing?? Is there anything missing in customization??

Thanks in advance

Suraj