SE71: Copy form b/w clients

SAP Script experts,

There is a transport request in source system which has say 10 forms, I use SE71 to copy from source to target, I also check whether form exists in souce, positive.

Now when copying the form from one client to another it gives me an error message:

Request/task <> has invalid source client <>.

Log says:

Problem calling the transport system and Workbench Organizer

Any pointers as to what could be the issue.

Thanks.