Recovery from easy-rsa vm failed

Hello,
i am in big trouble :(
we make our keys for openvpn (2.1.1) within an fully Truecrypt encrypted Windows XP SP3 VM (VMWARE Workstation).
Today i made some mistaks. I wanted to make an new client key, but unfortunately i typed "build-ca [username]".
I copy the complete VM from the latest backup. But now i get when i build-key.bat:

CA certificate and CA private key do not match
4028:error:0B080074:x509 certificate routines:X509_check_private_key:key values
mismatch:.\crypto\x509\x509_cmp.c:406:
c:\programme\OpenVPN\easy-rsa\keys*.old could not be found

I tried an older backup… same error.

Recognize any changes in hardware?

Please help me. 1000thanks

yours sincerly

Andi