Internet Explorer 9 Navigation blocked due to invalid certificate 1024 bit

Had a problem where IE9 would not open a web page, whereas IE10 would. Web page is the management site for an HP StorOnce B6200 appliance.

Looks like the StorOnce appliance is using a 1024 bit public key, and IE9 doesn't like this. The certificate is self signed, and you get the normal error, but the "Continue to this website (not recommended)." link is not available:

I did some Googling and found this.

I ran certutil -setreg chain\EnableWeakSignatureFlags 8.

I didn't have to reboot, just logged out and in, and the Web page changed:

I will investigate a longterm fix of adding a proper certificate (we have internal certificate servers) or public certificate. I'll also approach HP about icreasing the public key length from 1024 to 2048 bits.