How to prevent the minibuffer from being cleared?

[hester@informatik.uni-wuerzburg.de (Christian Hestermann)]

Hi there!

Does anyone know how to prevent the mini-buffer of a Fred-window from being
cleared so often? For example: I type the name of a function, and after the
first blank I get a short form of the parameters to that function. Very
convenient. Then I type the first letter of the first argument, and the
information is gone. It is not replaced with something more interesting but
just with spaces. Very annoying. I've tried to change 'set-mini-buffer' but
'mini-buffer-update' seems to be called from something else, too. I want
the mini-buffer to be updated only with something unlike an empty string. 

By the way: The Fred-command 'ed-push/pop-mark-ring' doesn't behave,
either. I'd like to mark the current place in a file, move the cursor
somewhere else, and finally send it back to the mark previously set. I hate
to look for the place I want to continue my work after looking up something
else (like a function-definition or so). 

Thanks for any hints!

Christian Hestermann
Lehrstuhl Informatik VI
Univ. Wuerzburg
Allesgrundweg 12
W-8708 Gerbrunn, Germany