If you upgraded to KDE 4.6.5 from Eric Hameleers and you have been using KCalc, you might have noticed that it doesn't accept inputs from the keyboard and only works with mouse clicks. This is a regression found on KDE 4.6.5 and also in the development version of KDE 4.7, so it's not Eric's fault. It's upstream code, and not due to compilation process.
If you want to fix this, you will have to recompile kdeutils package with the patch described on KDE Bug Tracking System.
Actually i realized this few days ago and i thought there was a problem with my keyboard, but today i realized that it was a regression from the upstream code itself and it's not my keyboard's whose faulty