Hi, I detect problem in mod_dav_svn or mod_dav_svn_authz.
If enabled mod_evasive, problems with authorization to subversion.

vhosts.conf
--- Skip config ---
<VirtualHost [cut IP-address]>
      ServerName [cut sever name]
     ServerAdmin [cut e-mail]
     <Location />
         DAV svn
         SVNPath [cut path to svn directory]
         AuthType Basic
         AuthName "Developement SVN server"
         AuthUserFile /etc/apache2/dav_svn.passwd
         Require valid-user
     </Location>
     LogLevel debug
     ErrorLog "/var/log/apache2/error.log"
     CustomLog "/var/log/apache2/access.log" combined
</VirtualHost>
--- Skip config ---

error.log
--- Skip log ---
[Mon Oct 11 16:17:19 2010] [debug] mod_deflate.c(615): [client<cut IP-address>] Zlib: Compressed 202 to 161 : URL /
[Mon Oct 11 16:20:59 2010] [debug] mod_deflate.c(615): [client<cut IP-address>] Zlib: Compressed 401 to 272 : URL /
[Mon Oct 11 16:21:15 2010] [debug] mod_deflate.c(615): [client<cut IP-address>] Zlib: Compressed 179 to 123 : URL /
[Mon Oct 11 16:21:15 2010] [debug] mod_deflate.c(615): [client<cut IP-address>] Zlib: Compressed 629 to 316 : URL /
[Mon Oct 11 16:21:15 2010] [debug] mod_deflate.c(615): [client<cut IP-address>] Zlib: Compressed 382 to 220 : URL /!svn/vcc/default
[Mon Oct 11 16:21:15 2010] [debug] mod_deflate.c(615): [client<cut IP-address>] Zlib: Compressed 437 to 234 : URL /!svn/bln/696
[Mon Oct 11 16:21:17 2010] [debug] mod_deflate.c(615): [client<cut IP-address>] Zlib: Compressed 629 to 316 : URL /
[Mon Oct 11 16:21:17 2010] [debug] mod_deflate.c(615): [client<cut IP-address>] Zlib: Compressed 382 to 220 : URL /!svn/vcc/default
[Mon Oct 11 16:21:17 2010] [debug] mod_deflate.c(615): [client<cut IP-address>] Zlib: Compressed 437 to 234 : URL /!svn/bln/696
[Mon Oct 11 16:21:17 2010] [debug] mod_deflate.c(615): [client<cut IP-address>] Zlib: Compressed 629 to 316 : URL /
[Mon Oct 11 16:21:17 2010] [debug] mod_deflate.c(615): [client<cut IP-address>] Zlib: Compressed 437 to 234 : URL /!svn/vcc/default
[Mon Oct 11 16:21:17 2010] [debug] mod_deflate.c(615): [client<cut IP-address>] Zlib: Compressed 641 to 321 : URL /!svn/bc/696
[Mon Oct 11 16:21:17 2010] [debug] mod_deflate.c(615): [client<cut IP-address>] Zlib: Compressed 401 to 272 : URL /
[Mon Oct 11 16:21:17 2010] [debug] mod_deflate.c(615): [client<cut IP-address>] Zlib: Compressed 179 to 123 : URL /
[Mon Oct 11 16:21:17 2010] [debug] mod_deflate.c(615): [client<cut IP-address>] Zlib: Compressed 629 to 316 : URL /
[Mon Oct 11 16:21:17 2010] [error] [client<cut IP-address>] client denied by server configuration: /etc/apache2/htdocs
--- Skip log ---

Thanks!

[sysadmin@gorod0k.ru]

I haven't investigated this in detail, but Subversion libsvn_neon
(client side) and mod_dav_svn (server side) implement a rather
inefficient protocol.  Accomplishing anything requires too many queries
and too many round trips.  It is possible that mod_evasive is noticing
these patterns and mistaking them for a DoS attack.

Subversion 1.7, when it comes out (early next year, perhaps) will have
a redesigned, more streamlined, HTTP-based protocol.  This will only be
used when both client and server are running 1.7, of course, but I
expect it may solve this bug.

Thanks for the report,
Peter