Pop up the Run Command window (Alt+F2 by default) and type:

You can also enter any of these in the Location text box in Konqueror.

Or you can use the KDE Help Center if you are using KDE 2. Simply start the KDE Help Center by clicking on the icon (the blue book with the yellow key) on the toolbar. Once the KDE Help Center has loaded, the window on the left will contain an entry called Unix manual pages. Click once on this entry, and you can browse through all the installed manual pages on your system.

To move a window, use Alt+left mouse button. Alt+right mouse button will resize the window. Last but not least, Alt+middle mouse button raises/lowers the window. The KDE Control Center allows you to change these mouse bindings.

There is a standard keybinding (Ctrl+Alt+Esc) that gives you a skull & crossbones cursor. Click that cursor on a window to kill it. The keybindings are viewable/changeable from the KDE Control Center.

These kind of locks tend to occur when an application locks up while it has a so called “mouse/keyboard grab”. When that happens you can try to select a virtual text console with Ctrl+Alt+F1 and login. With the following command you will get a list of all running processes:

        ps -aux | more

By killing the process that has the mousegrab, your desktop will come to life again. Unfortunately you can't see which process that is, so you will have to find out through trial and error. To kill a process use:

        kill -9 pid

Here pid is the process id of the process, which is the first number on each line reported by ps -aux.

You can switch back to the desktop with Ctrl+Alt+F7 (or F8 through F9 depending on your operating system) to see if things work again. When you press Alt+Tab you should get a response from the window manager. If not, you need to get back to the text console and try to kill another process.

Good candidates to kill are: the application you were working with, Kicker, Klipper and KDesktop.