R – CruiseControl.Net Failed Build – No explanation

I am just beginning to set up a Continuous Integration Server using CruiseControl.Net. To keep things simple to begin with, I used the Visual Studio Task to carry out the build, pointing it at the project solution file. However, when the build process occurs, CC.Net successfully gets the latest source version from Subversion, and appears to run the devenv command. The build process then fails, but there is no explanation about why. Here is the output:

BUILD FAILED
Project: MyProject
Date of build: 2009-09-09 16:31:13
Running time: 00:00:49
Integration Request: Dashboard triggered a build (ForceBuild)

Modifications since last build (0)

Tests run: 0, Failures: 0, Not run: 0,
Time: 0 seconds No Tests Run This
project doesn't have any tests

There is nothing else displayed on the page. My XML Logs don't show any build results either.

This is my configuration file:

<!--<ccnetconfig><configurationVersion>1.4</configurationVersion></ccnetconfig>-->
<cruisecontrol>
  <project name="MyProject">
    <workingDirectory>C:\Users\Builder\Desktop\builder-pc\MyProject</workingDirectory>
    <sourcecontrol type="svn">
      <trunkUrl>svn://builder-pc/MyProject/trunk</trunkUrl>
      <workingDirectory>C:\Users\Builder\Desktop\builder-pc\MyProject</workingDirectory>
      <executable>C:\Program Files\Subversion\bin\svn.exe</executable>
      <autoGetSource>True</autoGetSource>
      <tagOnSuccess>True</tagOnSuccess>
    </sourcecontrol>
    <tasks>
      <devenv>
        <solutionfile>C:\Users\Builder\Desktop\builder-pc\MyProject\trunk\MyProject.sln</solutionfile>
        <configuration>release</configuration>
        <buildtype>Rebuild</buildtype>
        <executable>C:\Program Files\Microsoft Visual Studio 9.0\Common7\IDE\devenv.exe</executable>
        <buildTimeoutSeconds>600</buildTimeoutSeconds>
      </devenv>
    </tasks>
  </project>
</cruisecontrol>

I have deliberately removed things like the SVN username and password.

Building the solution using the VS Command Prompt works, albeit with warnings. This is using the same swtiches that CC.Net would be using.

Can anyone help? Is it failing because there are no unit tests to run, or because of the warnings? Or is it best to switch to MSBuild or NAnt instead of using the Visual Studio Task?