Really at a loss here...my Dreamer started grinding terribly when printing and I can't pinpoint what this noise is. You can hear it at the 24 second mark in this video.

At first I thought that the print bed had somehow raised above the level of the nozzles, but that's not it -- I lowered the thumbscrews until the bed was well clear of the nozzles, then leveled. It doesn't appear that the nozzles are touching the glass.

Any pointers would be greatly appreciated; I'm not at all comfortable running the printer when this is happening.