The guy at my LHBS said he thought it was just some dead yeast that's decided to float instead of sink. He had a taste of one and confirmed it wasn't infected and tasted as it should. He said with age the bits should settle, and also if you give them a shake and then chill them the bits will sink. We did this and they actually did seem to disappear. Doesn't mean they aren't still there though...
If it was yeast then why would you be only having this occur in one fermentor! <_<
Hirns