Combo box field type doesn't work in MODX 3

[SnowCreative]

I've got Collections 4 installed on a couple of sites running MODX 3 (some in 3.0.3, some in 3.0.4 dev), and the combox box option isn't work. All existing tags show up in the field as plain text separated by commas, and selecting a new tag through the popup replaces the entire list with that one tag.

The tags should show up as individual tags like buttons, with Xs to delete each one.

[SnowCreative]

Aargh. Sorry, submitted this to the wrong Extra! Please delete.