Paradox 10 seems to have some to the connection to the keyboard, which has worked for many years. While the space key for date entry, up, down, enter, search and tap keys continue to function correctly, function keys do not. F8 for form development, F9, edit mode and insert for queries do not function.
I do queries by idiot interface (not being at all good at programming), and cannot find an alternative to the insert key..otherwise there are workarounds.

Is there any explanation and fix for this apart from reinstallation?

I have never heard of this issue before.. what version of windows? have you looked at the hot key stuff in the shortcut properties and in control panel? have you tried a different keyboard and/or keyboard driver?