Unable to import certificate using APC Security Wizard

[Anonymous user]

We've recently upgraded to IE 10, and have hit this certificate problem: http://support.microsoft.com/kb/2661254

Accordingly, I've found this guide on APC's site to update the NMC certificate to 1024 bit: http://www.apcmedia.com/salestools/ASTE-6Z5QF2/ASTE-6Z5QF2_R2_EN.pdf

I've generated the private key and CSR, and used the CSR to generate a new cert.  I've then downloaded the resulting cert in both DER and Base64 format (the guide doesn't specify which it needs).

However, no matter which cert I use, when I use the wizard to Import the certificate with the private key file, I get: Error importing cert, code: -32.

I can't seem to find any information about what the error code means.  Can someone help?