Build update site error

I kept getting this error when I tried to build an update site for deploying a prototype application to jazz server (I followed the deployment wiki session in the HelloJFS osgi example).

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"Build Site" has encountered a problem:

C:\Projects\RMC\RMC7.5.2.2-Server\.metadata\.plugins\org.eclipse.pde.core\temp\org.eclipse.pde.container.feature\assemble.org.eclipse.pde.container.feature.p2.xml:35: The following error occurred while executing this line:
C:\Projects\RMC\RMC7.5.2.2-Server\.metadata\.plugins\org.eclipse.pde.core\temp\org.eclipse.pde.container.feature\assemble.org.eclipse.pde.container.feature.p2.xml:166: Unable to find: Installable Unit [ id=com.ibm.team.jfs.sdk.runtime.feature.feature.group version=1.2.0.v20120522_2345 ]
The following error occurred while executing this line:
C:\Projects\RMC\RMC7.5.2.2-Server\.metadata\.plugins\org.eclipse.pde.core\temp\org.eclipse.pde.container.feature\assemble.org.eclipse.pde.container.feature.p2.xml:166: Unable to find: Installable Unit [ id=com.ibm.team.jfs.sdk.runtime.feature.feature.group version=1.2.0.v20120522_2345 ]
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This error did not occur occasionally, and the build was somehow successful once. I was not sure what was causing this, any tool initialization that I need to do, or cache issue that I need to clear?

It seems to be associated with including the com.ibm.team.jfs.sdk.runtime.feature in my update site.

Is it a bug with pdf build tool? Any help or hint for work-around would be greatly appreciated.

Thanks,

Weiping