Restore default CA Certificates on Mac OSX 10.7

Question

I've been screwing around with my Mac, trying to install self-signed certificate as trusted for our WAN site (for which we can't justify paying for a real signed certificate)

I've broken something and would like to know how to restore (even from another Mac, if it needs be, I have a fully-functional Macbook I haven't broken yet, and the machines of my colleagues).

Here's what I get trying to use curl to download something over SSL:

$ brew install memcached
==> Installing memcached dependency: libevent
==> Downloading https://github.com/downloads/libevent/libevent/libevent-2.0.16-stable.tar.gz

curl: (60) SSL certificate problem, verify that the CA cert is OK. Details:
error:14090086:SSL routines:SSL3_GET_SERVER_CERTIFICATE:certificate verify failed
More details here: http://curl.haxx.se/docs/sslcerts.html

curl performs SSL certificate verification by default, using a "bundle"
 of Certificate Authority (CA) public keys (CA certs). If the default
 bundle file isn't adequate, you can specify an alternate file
 using the --cacert option.
If this HTTPS server uses a certificate signed by a CA represented in
 the bundle, the certificate verification probably failed due to a
 problem with the certificate (it might be expired, or the name might
 not match the domain name in the URL).
If you'd like to turn off curl's verification of the certificate, use
 the -k (or --insecure) option.
Error: Download failed: https://github.com/downloads/libevent/libevent/libevent-2.0.16-stable.tar.gz