It seems that I am running into the same problem but with linux operationg system. The keys seem to have been accepted perfectly but when I want to conduct a backup I get the 500 error message.
Server:
Linux home 2.6.34-hardened-r6
PHP Version 5.2.14-pl0-gentoo
Gentoo Linux mysql-5.0.90-r2
WP 3.4.1
Client:
Chrome / Windows7
