Repairing a damaged Resource file

I really REALLY need help in restoring a VC++ resource file. I
changed a string in the string table and then I got the
<Cannot change standard MFC resources> error of death.

Now my project is a total nightmare.

When trying to fix this error, I'll get a problem with IDC_MAINFRAME (I think that was the error) and I get these linker errors too:

fatal error CVT1100: duplicate resource -- type GROUP_CURSOR, name:30978 language 0x0409
Failure during converstion to COFF: file invalid or corrupt

How do I restore this?