It might also be the detergent you're using, I can't remember the name, either Bold or Surf, but if you're using a different detergent for the baby's clothes and things, that may be the culprit. There is a detergent here that - to my nose, anyway - has this musty, dank sort of smell to it, drives me nuts when I smell it, and it also lingers, it's strong. If it turns out that the spit up isn't the culprit, maybe it's this?