Version:           1.1 (using KDE 3.5.7, Kubuntu (gutsy) 4:3.5.7-1ubuntu3)
Compiler:          Target: i486-linux-gnu
OS:                Linux (i686) release 2.6.22-6-generic

If i delete a to-do item from the top of the list and then modify the summary view of to-do, the deleted items reappear.

Here are the steps to reproduce:

1) Open the to-do list view in kontact.
2) create a new to-do by typing into the top bar. Type something like "AAA" so 
that it would appear on top of the list (assuming it is sorted by the summary 
column)
3) Switch to to the summary view. You will notice that it now appears here.
4) Switch back to the to-do view. select the to-do "AAA" and hit delete.
5) Switch back to summary view. You will notice that it is gone as expected.
6) While in the summary view, select Settings->configure summary 
view->appointments and to-dos.
7) Select "Today's to-dos only" instead of "Show all to-dos" and click apply.
8) Now select "Show all to-dos" and click OK. "AAA" again appears in the 
summary view.
9) switch to To-do view and it is not there.
10) Quit kontact and launch it again and "AAA" will be there in the summary 
and the to-dos view.