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.