Error when starting submethod -

Dear Experts,

we are using standard work flow for Appropriation Request(AR) approving.

Approvers are geting mail to SAP inbox.

when double click on inbox->worlflow item for that particular AR, it goest AR display screen & when we click on balk(F3) goes to screen where we can click on "approve" , " Reject" buttons.

now issue is once double click on inbox item gives infor message saying "Error when starting submethod"(Message no. SWF_RUN637) & goes to approval screen directly.

Please help to correct this issue.

Thanks & kind Regards,

SL