<p>When I launch CruiseControl.NET with a particular configuration file I receive the following error:</p>

<blockquote>
  <p>ThoughtWorks.CruiseControl.Core.Config.ConfigurationException: Duplicate node detected</p>
</blockquote>

<p>What does this mean, and what causes it?</p>

No, I don't believe so.
Certainly the C# compiler disallows it when converting a lambda expression:
```
```
int x;
Expression<Func<int,int>> foo = (x=y); // Assign to x and return value
```
```
This yields the error:
```
```
CS0832: An expression tree may not contain an assignment operator
```
```