Problem when setting SVN by using Apache2

Hello,
I have compiled and installed SVN 1.4.4 and want to configure it to run by
using apache2. (On Ubuntu 7.04)
I followed the book <Version Control with Subversion> and apache2
successfully started up with svn mods. My configuration in httpd.conf is
like below:
<Location /svn>
    DAV svn
    SVNParentPath /var/svnroot
    SVNListParentPath on
    AuthType Basic
    AuthName "Subversion repository"
    AuthUserFile /etc/svn-auth-file
    Require valid-user
</Location>

My apache is started as apache:apache user so I change the owner of
/var/svnroot from root to apache.apache.
Then I use:
svn import dummy.test http://localhost:8088/svn/test -m "test"
to create the very first test. But after I input the password I got:
svn: PROPFIND request failed on '/svn/test'
svn: Could not open the requested SVN filesystem

In apache2 error logs I found:
[Tue Aug 07 01:00:02 2007] [error] [client 127.0.0.1] (20014)Internal error:
Can't open file '/var/svnroot/test/format': No such file or directory
[Tue Aug 07 01:00:02 2007] [error] [client 127.0.0.1] Could not fetch
resource information. [500, #0]
[Tue Aug 07 01:00:02 2007] [error] [client 127.0.0.1] Could not open the
requested SVN filesystem [500, #2]
[Tue Aug 07 01:00:02 2007] [error] [client 127.0.0.1] Could not open the
requested SVN filesystem [500, #2]

Then I use:
sudo svnadmin create /var/svnroot/dummy
It seems successful to create a repository because in my browser when I
visit "http://localhost:8088/svn/dummy" I can get a page of which content is
like:
Revision 0: /
------------------------------
*Powered by Subversion <http://subversion.tigris.org/> version 1.4.4(r25188).
*

So I don't know why I cannot import a file. I google this for a long time
but cannot find useful information...
Thanks for helping!

-- 
Zhang Xiao
Engineer, LAMP Team
Ethos Tech.
http://www.ethos.com.cn