After creating a CSR locally via Keychain Access, attempts to upload for signing via the safari dev program website fail. With the latest Safari release, the website operated correctly, however with WebKit nightlies the website reported that the file was corrupt or in an incorrect format. The most recent nightly I tried was r71204, immediately following success submitting the same CSR file via Safari 5.0.2. I do not have any ideas of what the failure may have been, and did not see anything reported in the error console. I'm open to gather additional information or perform additional troubleshooting with guidance.
<rdar://problem/8629437>
I believe this was fixed by http://trac.webkit.org/changeset/74427. You should be able to verify this with the most recent WebKit nightly build (r75891).