Version:            (using Devel)
Installed from:    Compiled sources

In many cases the input fields are corrupted in konqueror. Like on the bugs.kde.org login fields. It doesn't happen always, but try to enter a user name and passwd and click between the fields with the mouse. Sooner or later the first part of the user name will be covered with a white rectangle. If it doesn't happen, try to use a form with autocompletion text or go to a page where the fields are automatically completed. Here is a screenshot:
http://andras.kdewebdev.org/other/inputbug.png

The interesting part is the missing first two digits, the corrupted 0 and the grey background for 61. By clicking on the field, the background changes in various ways (full grey, part grey, visible text or corrupted text and so on).
Happens with both oxygen and plastique.