[MonetDB-users] copy into with primary key errors

I've been trying to bulk load a large set of data into a table with a compound primary key. Every time the copy into fails on the second file with an error about an "invalid input type". Even if I comment out the suspect file, the third file with have the same error. If I repeat the load and comment out the first file, then the third file will have the "invalid input type" error. Has anyone been able to use COPY INTO with a compound primary key and multiple files?