rSmart dev server
SmartSite@UCDavis - 2.6.4.0 - Sakai 2.6.2 - Server "ucddev1"
• This server is now running tag 1.3.0-rc3 for Gradebook2
• This server is now running rsmart's CLE at r21686

STEPS TO REPRODUCE PROBLEM -
1 - create an item
2 - enter a due date in format 9-15-2010 and save
3 - the date box will be outlined in red because of the incorrect format
4 - correct the date to format 9/15/2010

you can't save it. the "save" and "save and close" boxes are greyed out.
if you close and re-edit the item, the date will be gone. AND the boxes
are still greyed out. they don't even come back if you enter the date
in the correct format.

I can't get them back until I edit another item and return to the first.
I think you should be able to correct the problem and save back at step 4.