Dificuldade para utilizar o maven-release-plugin

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
   xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">

   <modelVersion>4.0.0</modelVersion>
   <groupId>...</groupId>
   <artifactId>buit</artifactId>
   <version>1.0.0-SNAPSHOT</version>
   <packaging>pom</packaging>
   
   <scm>
      <url>repo</url>
      <connection>scm:svn:repo</connection>
      <developerConnection>scm:svn:repo</developerConnection>
   </scm>

   <modules>
      <module>modulo-1</module>
      <module>modulo-2</module>
   </modules>

   <dependencies>
      <dependency>
         <groupId>junit</groupId>
         <artifactId>junit</artifactId>
         <version>4.10</version>
         <scope>test</scope>
      </dependency>
   </dependencies>

   <build>
      <plugins>
         <plugin>
            <groupId>org.apache.maven.plugins</groupId>
            <artifactId>maven-compiler-plugin</artifactId>
            <version>2.0</version>
            <configuration>
               <source>1.6</source>
               <target>1.6</target>
            </configuration>
         </plugin>
         
         <plugin>
            <groupId>org.apache.maven.plugins</groupId>
            <artifactId>maven-release-plugin</artifactId>
            <configuration>
               <tagBase>repo/tags/buit/releases</tagBase>
               <autoVersionSubmodules>true</autoVersionSubmodules>
            </configuration>
         </plugin>
      </plugins>
      
   </build>
</project>

[INFO] BUILD FAILURE
[INFO] ------------------------------------------------------------------------
[INFO] Total time: 2.341s
[INFO] Finished at: Tue Feb 14 13:31:48 GMT-03:00 2012
[INFO] Final Memory: 10M/164M
[INFO] ------------------------------------------------------------------------
[ERROR] Failed to execute goal org.apache.maven.plugins:maven-release-plugin:2.0:prepare (default-cli) on project buit: Unable to check for local modifications
[ERROR] Provider message:
[ERROR] The svn command failed.
[ERROR] Command output:
[ERROR] svn: E155036: Please see the 'svn upgrade' command
[ERROR] svn: E155036: Working copy 'workspace-path' is too old (format 10, created by Subversion 1.6)
[ERROR] -> [Help 1]
[ERROR] 
[ERROR] To see the full stack trace of the errors, re-run Maven with the -e switch.
[ERROR] Re-run Maven using the -X switch to enable full debug logging.
[ERROR] 
[ERROR] For more information about the errors and possible solutions, please read the following articles:
[ERROR] [Help 1] http://cwiki.apache.org/confluence/display/MAVEN/MojoFailureException
[ERROR] 
[ERROR] After correcting the problems, you can resume the build with the command
[ERROR]   mvn <goals> -rf :buit