What would cause a "ResGen : error RG0000" error in VS2010?

When I build my Windows form application, I'm getting following errors. Can someone tell me what could be wrong?

ResGen : error RG0000: Could not load referenced assembly "\.....\bin  
\Debug\PlugingCommon.dll".  Caught a FileNotFoundException saying 
"Could not load file or assembly '\...\PluginSource.dll' or one of its 
dependencies. The system cannot find the file specified.".      

ResGen : error RG0000: Could not load referenced assembly "\...\bin 
\Debug\MetadataField.dll".  Caught a FileNotFoundException saying 
"Coul开发者_高级运维d not load file or assembly '\...\bin\Debug\MetaField.dll' or 
one of its dependencies. The system cannot find the file specified.". 

There are several such bugs in the solution.

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I'd say the problem is that your system cannot find the files MetaField.dll or PluginSource.dll.
It's kinda glaringly obvious if you think about it.