set process-connection-type to nil breaks gnus and erc

[Xiao-Yong Jin]

Hi, I came to a problem recently.  Because I tried to fix
echoing in haskell-mode/ghci process in emacs, I put

(setq process-connection-type nil)

in my ~/.emacs.  But after this, I can no longer start gnus
and erc.  Both gnus and erc just hang there indefinitely.  I
can do a C-g to interrupt gnus, but with erc, C-g doesn't
work and I need to kill emacs.

So it looks like a very dangerous variable to me.  Can
someone explain what is going on?  Is it a bug?  I'm using

"GNU Emacs 23.0.91.1 (x86_64-unknown-linux-gnu, GTK+ Version 2.14.7)
 of 2009-03-21 on tux"

Thanks,
Xiao-Yong
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