If you create a checkout with a due date in the past (I selected 2011-08-15), and try to check-in, the script keeps waiting forever. Teh following error is shown: checkin: Invalid local time for date in time zone: America/Argentina/Cordoba I'll fill a specific bug for that error. This one is for the ajax not receiving the failure notice.
I can't reproduce this problem in 3.23.00.031. Here's what I tried: 1. Checked out an item, setting the due date to a date in the past. 2. In the updated list of checkouts I checked the checkbox in the "Check in" column and submitted. The AJAX check-in operation completed successfully.
That has certainly been fixed by a previous patches.