In poking around at the svn backend I found that the svn post-commit 
hook calls to svn update fail regularly with an error code of 256. 
Apparently during the post-commit hook can't update because the 
working copy is locked from the commit. Since the post-commit hook doesn't send
errors anywhere and svn update runs with --quiet anyhow, this error
isn't usually visible, but on my system:

    ethan@sundance:~/tests/webtemplates/ikiwiki3/wc$ svn commit -m "Blah.."
    Sending        index.mdwn
    Transmitting file data .
    Committed revision 3.

    #verifying output was created
    ethan@sundance:~/tests/webtemplates/ikiwiki3/wc$ less ../dest/index.html 

    ethan@sundance:~/tests/webtemplates/ikiwiki3/wc$ svn info
    Path: .
    URL: file:///home/ethan/tests/webtemplates/ikiwiki3/svn/trunk
    Repository Root: file:///home/ethan/tests/webtemplates/ikiwiki3/svn
    Repository UUID: f42bb0d6-3c1e-0410-b2d4-aeaad48dd6c4
    Revision: 2
    Node Kind: directory
    Schedule: normal
    Last Changed Author: ethan
    Last Changed Rev: 2
    Last Changed Date: 2006-09-24 21:15:55 -0400 (Sun, 24 Sep 2006)

A sample error message (obtained through file redirection) is:

    svn: Working copy '.' locked
    svn: run 'svn cleanup' to remove locks (type 'svn help cleanup' for details)

Did I do something stupid again or is this the case on your system too? 
--Ethan

Additional note: this doesn't happen when performing svn commits from another wc, 
but *does* happen when committing from the web.
--Ethan

> Yeah, this makes sense now that you bring it up. Perhaps I should make
> ikiwiki skip the update when called from the post-commit hook if the repo
> is locked, although this could mask other problems.. --[[Joey]]

>> I don't think it's (yet) a serious problem, because any commit to the repo
>> either comes from another WC, in which case, no problem, or it is committed by 
>> ikiwiki through its own WC, in which case that WC is "the newest". The only problem
>> is that ikiwiki's rcs information for web commits gets screwed up. I think the
>> correct fix is to call rcs_update from rcs_commit in svn.pm, if 
>> the commit succeeds. I'm not sure whether this ought to happen for all RCSes
>> or just svn. --Ethan