Does it happen every time you run it, or just happened once at some random time?

I've never seen that fail before.  It's a call to OpenSSL that I assumed would never fail, but I put an error check there just in case.  I can't imagine how it would fail.  Out of memory maybe.

The code is:

key.h:
    EC_KEY* pkey;

        pkey = EC_KEY_new_by_curve_name(NID_secp256k1);
        if (pkey == NULL)
            throw key_error("CKey::CKey() : EC_KEY_new_by_curve_name failed");

NID_secp256k1 is a constant.