why do CollabNet Subversion Client and TortoiseSVN both update projects fine, but <svn> <update> within Ant fails

I can manually update individual projects using CollabNet or Tortoise no problem.

But my ant开发者_开发问答 script (executed from Hudson) containing

<svn javahl="false" svnkit="false" username="${svn.username}" password="${svn.password}">
    <update dir="${dest.path}/@{project}" />
</svn>

fails with

[svn] svn: 'C:\Hudson-slave\xxxxx\yyyyy' is not a working copy

[svn] svn: Cannot read from 'C:\Hudson-slave\xxxxx\yyyyy.svn\format': C:\Hudson-slave\xxxxx\yyyyy.svn\format (The system cannot find the file specified)

[svn] failed !

Could ant be using and older version of svn? How can I check which version it's using?

I'd use Process Explorer to look at the exact SVN command being run by ant. You should then be able to replicate the problem outside of ant.