PluginPackager exited with code 99

PluginPackager exited with code 99

Using the ocean wizard I have generated a pip project and am now trying to
build it after adding things to the DeployList.xml. However I then get the
following message: The command ""%OCEAN2013HOME%\PluginPackager.exe" /p
"C:\ext_source\ext_6_1_2013\ocean\IkonRockPhysicsWorkflowPIP2013\obj\copytemp\IkonSyntheticsPlugin.dll"
"C:\ext_source\ext_6_1_2013\ocean\x64\Release\IkonRockPhysicsWorkflowPIP2013.pip""
exited with code 99.
Does anybody know what this code means and how to fix it? The other pip
project builds just fine and includes exactly the same contents except for
two dll's. Removing these two dll's still does not work.