System.NullReferenceException when using MSBuild deployment with a Package

I'm getting an exception while deploying a package from command line:

Microsoft (R) Build Engine Version 2.0.50727.3053
[Microsoft .NET Framework, Version 2.0.50727.3053]
Copyright (C) Microsoft Corporation 2005. All rights reserved.

Build started 7/17/2009 2:58:50 PM.
__________________________________________________
Project "C:	empMYAPPLICATIONDeploymentMyPackageName.msbuild" (default targets):

Target Deploy Processes:
    __________________________________________________
    Project "C:	empMYAPPLICATIONDeploymentMyPackageName.msbuild" is building "C:	empMYAPPLICATIONDeploymentMyPackageName.msbuild" (InitDeploy target(s)):

    C:	empMYAPPLICATIONDeploymentMyPackageName.msbuild(82,5): error MSB4018: The "SourceCode.DeploymentTasks.ExportProcessTask" task failed unexpectedly.
    C:	empMYAPPLICATIONDeploymentMyPackageName.msbuild(82,5): error MSB4018: System.NullReferenceException: Object reference not set to an instance of an object.
    C:	empMYAPPLICATIONDeploymentMyPackageName.msbuild(82,5): error MSB4018:    at SourceCode.DeploymentTasks.DeploymentTask.Initialize()
    C:	empMYAPPLICATIONDeploymentMyPackageName.msbuild(82,5): error MSB4018:    at SourceCode.DeploymentTasks.ExportProcessTask.Initialize()
    C:	empMYAPPLICATIONDeploymentMyPackageName.msbuild(82,5): error MSB4018:    at SourceCode.DeploymentTasks.Task.set_BuildEngine(IBuildEngine value)
    C:	empMYAPPLICATIONDeploymentMyPackageName.msbuild(82,5): error MSB4018:    at Microsoft.Build.BuildEngine.TaskEngine.InitializeTask(ITask task, ItemBucket bucket)
    C:	empMYAPPLICATIONDeploymentMyPackageName.msbuild(82,5): error MSB4063: The "SourceCode.DeploymentTasks.ExportProcessTask" task could not be initialized with its input parameters.
Done building target "Deploy Processes" in project "MyPackageName.msbuild" -- FAILED.

Done building project "MyPackageName.msbuild" -- FAILED.

Build FAILED.
C:	empMYAPPLICATIONDeploymentMyPackageName.msbuild(82,5): error MSB4018: The "SourceCode.DeploymentTasks.ExportProcessTask" task failed unexpectedly.
C:	empMYAPPLICATIONDeploymentMyPackageName.msbuild(82,5): error MSB4018: System.NullReferenceException: Object reference not set to an instance of an object.
C:	empMYAPPLICATIONDeploymentMyPackageName.msbuild(82,5): error MSB4018:    at SourceCode.DeploymentTasks.DeploymentTask.Initialize()
C:	empMYAPPLICATIONDeploymentMyPackageName.msbuild(82,5): error MSB4018:    at SourceCode.DeploymentTasks.ExportProcessTask.Initialize()
C:	empMYAPPLICATIONDeploymentMyPackageName.msbuild(82,5): error MSB4018:    at SourceCode.DeploymentTasks.Task.set_BuildEngine(IBuildEngine value)
C:	empMYAPPLICATIONDeploymentMyPackageName.msbuild(82,5): error MSB4018:    at Microsoft.Build.BuildEngine.TaskEngine.InitializeTask(ITask task, ItemBucket bucket)
C:	empMYAPPLICATIONDeploymentMyPackageName.msbuild(82,5): error MSB4063: The "SourceCode.DeploymentTasks.ExportProcessTask" task could not be initialized with its input parameters.
    0 Warning(s)
    2 Error(s)

Time Elapsed 00:00:00.85

I'm running the following command (from exemple of the documentation)

msbuild "absolutepath	ofile.msbuild" -p:Environment=EnvironmentName

Any idea if there is something wrong, what to check?