We have been testing with this version (https://github.com/timkurvers/as3-crypto) on our internal LAN ever since I found it, but when I take it out to the internet and test with, say, Google talk, it doesn't work. The only way I can get it to work with Google talk is with the as3crypto.swc that was included with the nightly builds. So I'm thinking that .swc included with your distribution was not compiled with the Kurvers version you referenced. I even tried going back to the 1.3a Kurvers version in case a bug was introduced in 1.4.0 that he has as his latest.
So you may have replaced the as3crypt.swc you already had with a less patched version when you updated your Subversion at revision 13288 with the Kurves build. I cannot find any more update to date source code versions though, so I was thinking you may have one internally.