Using SQL Data Compare 10.2.3.5 on Win8, I opened an existing projected, that synchronized without error on 13 April 2013. A table change today was synchronized with SQL Compare. There are no differences in tables (but some in source db only).
When I attempt to compare, I am presented with a "Task cannot be completed" dialog with a X next to mapping. At the bottom of the dialog is the text "FieldMapping not valid for MatchingMapings.".
Of the twenty tables, all but one show a comparison key is set. The one table is "Not Set" (never has been as I do not wish to compare it). I have looked over the tables on the Mapping tab and all are mapped correctly.
I selected only one table, with one column, and receive same error. BTW, after error dialog closes, all tables are selected for compare - that is bad form; no need to do that if user has made selections. Additionally, any custom mappings I have made revert to use keys. But that is not my complaint.
I'd like to synch these databases, but not sure where to look (wish error message mentioned the able!). I created another project against two different databases on these servers and was able to compare.