Version:           2.8 (using KDE 4.6.4) 
OS:                Linux

First, the problem appeared in kde sc 4.6.5 and was not present in 4.6.4 (version 4.6.5 is not present in the "KDE Version" dropdown yet).
The problem is caused by the follwing commit:
http://websvn.kde.org/?view=revision&revision=1235447
The properties have been set on the shortcuts instead that on the label strings.
This causes the shortcuts not to work anymore, while other methods of input work fine (button press, paste, ..)

Reproducible: Always

Steps to Reproduce:
1) run kcalc
2) press the "ctrl" key: all the buttons should display their shortcuts
3) try to press a numeric key on the keyboard

Actual Results:  
at step 2) the digit buttons (0 to 9) display no shortcut
at step 3) nothing happens

Expected Results:  
at step 2) the digit buttons (0 to 9) should display their shortcuts
at step 3) nothing happens

reverting the fix or applying to the correct place will work. this patch has been applied to 4.7 too, it would be nice to have the fix in time for 4.7.0