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mfc30.lib could be either missing or corrupted - if I remember correctly you need Visual C++ Professional to have the MFC libraries installed - are you sure that its not VC++ 6 Standard edition on the machines where your project won't build.
An alternative is that the location of mfc30.lib is not in your linker input path. I would search the file-systems of the PC's where the app won't build to see if the mfc30.* files exist first, then go to project options to make sure they are on the linker input path.
Cheers,
Chris