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.

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.