Hi,
This is because of the BLANK ID in BW for which you have no MAPPING.
So kindly go through the POSSIBLE ERRORS section of the following document - BPC 10 NW InfoObj hierarchy load - Error "Duplicate member ID"
where it mentions:-
"3. Notice in the error message below that it reads "Dimension member is an invalid member ID". There is an extra space between "member" and "is". It is very common practice in planning data to have a BLANK ID in BW even if it is a compounded characteristic. Make sure you cater for eliminating this in your conversion. A statement like this in your *MAPPING section can help: ID=*IF(ID=*STR() THEN *STR(XXXX);ID=*STR() THEN *STR(XXXX);ID) i.e. direct the blank member to an equivalent value in BPC. "
Wish that helps...
Regards,
Bishwajit