Hi,
I did some testing, and the bug was not in tracker as I suspected, it's in
scrolltobottom, in erc-goodies.el. This should be much easier for you to
debug: it's only a few lines long. I strongly suspect the part following
this comment is responsible :
      ;; Temporarily bind resize-mini-windows to nil so that users who have
it
      ;; set to a non-nil value will not suffer from premature minibuffer
      ;; shrinkage due to the below recenter call.  I have no idea why this
      ;; works, but it solves the problem, and has no negative side effects.
      ;; (Fran Litterio, 2003/01/07)

Looks like it does have side effects after all :-)
2008/9/3 martin rudalics <rudalics@gmx.at>

> CC-ing Keegan because Bug #466 describes another problem with ERC and
> windows.
>
> >> There is a bug when using conjointly these two features. Here are the
> >> relevant portions of configuration :
> >>
> >> ;;make ibuffer resize itself to its buffer size
> >> (setq ibuffer-use-other-window t)
> >> (setq ibuffer-default-shrink-to-minimum-size t)
> >>
> >> No specific configuration for erc, just enabling tracker is enough.
> >> Then, run erc, and, in any erc buffer, call ibuffer. The screen
> >> briefly flashes as an ERC window opens then disappears, and the
> >> ibuffer window is reduced to a much smaller size than what it would be
> >> outside ERC. I think the issue is erc's hook to
> >> window-configuration-change somehow messing with ibuffer, but I'm not
> >> experienced enough to find where the bug is.
>
> Can't offer much insight but processing window-configuration-change
> hooks has changed with Emacs 23.  So this
>
> (defun erc-track-modified-channels ()
>  "Hook function for `erc-insert-post-hook' to check if the current
> buffer should be added to the modeline as a hidden, modified
> channel.  Assumes it will only be called when current-buffer
> is in `erc-mode'."
>  (let ((this-channel (or (erc-default-target)
>                          (buffer-name (current-buffer)))))
>    ...
>
> might have been broken for some reason.  To verify, someone would have
> to try with Emacs 22 and 23 inserting just before the `let' something
> like
>
> (unless (eq major-mode 'erc-mode)
>  (message "Not in erc-mode ..."))
>
> and look whether it triggers.
>
> martin
>
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