failed to import rule

[Parkinson]

Hey all-

I am getting an exception when I try to load one of the example rules into the packagebuilder.

the rule I am loading is:
package RulesEngine
rule "goodbye"
  when
    m : Message( status == Message.GOODBYE, message : message )
  then
    System.Console.Write(message);
    m.message ="Hey There";
end

rule "hello world"
  when
    m : Message( status == Message.HELLO, message : message )
  then
    System.Console.Write(message);
    System.Console.Write("\n");
    m.message= "Goodbye cruel world";
    m.status = Message.GOODBYE;
    modify( m );
end

the code doing the loading is:
        public void prepareRulesandWorkingMemory(String drlString)
        {
            PackageBuilder builder = new PackageBuilder();
            builder.AddPackageFromDrl(drlString);  //EXCEPTION GENERATED HERE
            Package pkg = builder.GetPackage();
            String errors = builder.GetPackage().GetErrorSummary();

            RuleBase ruleBase = RuleBaseFactory.NewRuleBase();
            ruleBase.AddPackage(pkg);

            workingMemory = ruleBase.NewWorkingMemory();
        }

and the exception I am getting is:
  at System.Reflection.Emit.AssemblyBuilder.get_Location()\r\n   at
org.drools.dotnet.semantics.DotnetCSharpCompiler.compile(String[]
pResourceNames, ResourceReader pReader, ResourceStore pStore,
ClassLoader pClassLoader) in
C:\\esahi\\drools.dotnet\\drools.dotnet\\semantics\\DotnetCSharpCompiler.cs:line
161\r\n   at org.drools.compiler.PackageBuilder.compileAll() in
PackageBuilder.java:line 469\r\n   at
org.drools.compiler.PackageBuilder.addPackage(PackageDescr
packageDescr) in PackageBuilder.java:line 209\r\n   at
org.drools.compiler.PackageBuilder.addPackageFromDrl(String fileName,
Reader reader) in PackageBuilder.java:line 128\r\n   at
org.drools.dotnet.compiler.PackageBuilder.AddPackageFromDrl(String
fileName, Stream drlStream) in
C:\\esahi\\drools.dotnet\\drools.dotnet\\compiler\\PackageBuilder.cs:line
78\r\n   at org.drools.dotnet.compiler.PackageBuilder.AddPackageFromDrl(Stream
drlStream) in C:\\esahi\\drools.dotnet\\drools.dotnet\\compiler\\PackageBuilder.cs:line
73

Any ideas as to what might be happening?