cannot type "
 

recently when I press " it doesnt type anything and after pressing it again it types ¨ and when i press ' it doesnt show anything and after repressing it it shows ´.
I am programming and I need ' and " but only using copy and paste from my old codes I can write these signs.
I am working on KDE and FC4

That is you are using a keyboard model or language other than plain english. On those keyboards/languages the keys are need to type accents.
Mine is portuguese. So, I can type áéíóúç etc...I can type ' ^ " too.
The trick is to type the accent key and space to get the symbol itself. Typing a symbol and a vowel in sequence, you get a accented vowel.

You can change the input model with a click, by using a keyboard applet in you Gnome or KDE desktop.

Bad keyboard?
Are all the other keys working OK?
In your system configuration, you might look at what keyboard mapping is being used. (I don't know where to find that in FC4)

everything is fine with other keys.i think i have had this problem since adding russian language layout.US english is my active layout.

I switched to gnome. I can type " and ' in gnome

This is a very interesting post. I have the same problem, typing the " once I hear a beep and no character is typed. Press it twice in succession and it works. The reason it is interesting is that it only occurs when I am using Debian. It does not occur in Slack, Fedora, etc. I am using a UK layout. Keyboard is brand new. The keys involved are the exact same keys described above.

Bob