The sales invoice line does not exist Identification field & values.. Error.

Dear Experts,

I am getting an error " The sales invoice line does not exist Identification field & values. Doc no " abc " Line No :"10000" 

while doing copy document in Credit memo form. I tried to debug but could not find the link. If any one has solved same issue than plz guide me ..The same error is seen in " Get Posted Document Lines to Reverse" After i select posted sales invoice .

Thanks a lot..