checkbox not firing event after checked is set programmatically

I am iterating through a string of characters and finding a checkbox. I find the checkbox without any problems and if the character of the iteration is equal to 't', I set the Checked property of the checkbox to true.

However, for whatever reason, although it does check the appropriate checkboxes, executing this code also means that when I click any checkbox myself, nothing happens. Also, the submit button on my page no longer does anything if I execute this code. I'm puzzled as to what may be the reason for this.

The buttons are created programmatically on init and are located inside an update panel.

DateTime date = new DateTime(2015, 11, 18);

foreach (char c in attendee.accommodation)
{
     ID = "accommodationCheckBox" + date.ToShortDateString();
     CheckBox checkbox = (CheckBox)FindControl(ID);
     if (checkbox != null && c == 't')
         {
             checkbox.Checked = true;
         }
     date = date.AddDays(1);
}