Hello, I've been using MonetDB for a couple of weeks now with no problems, but today ran into this issue when doing a series of DELETE/INSERT commands to update a table. When I issue the commands individually (autocommit on), there doesn't seem to be any difficulty, but when I do them as part of a transaction, I get this error on the second insert: START TRANSACTION; DELETE... 1 affected rows (10.145ms) INSERT... 1 affected rows (11.464ms) DELETE... 1 affected rows (3.402ms) INSERT... GDK reported error. BATsubselect: invalid argument: b must have a dense head I'm not sure what this means or what to do about it. Similar transactions were done yesterday with no problem, so I thought perhaps the table had been corrupted, but if I drop the table and recreate it from the original data, the above error still occurs. Thanks for any help you can provide, and if there is anything I can do that would give you some hints about what's happening, just tell me what to do and I'll be happy to help. Tim