[wp-testers] Weird behaviour with Ajax and .htaccess

[due chiacchiere]

Hello guys, just upgraded to 2.5 RC-3, and noticed a strange behaviour 
with my .htaccess settings. In order to block suspicious agents, I added 
these lines to my .htaccess

# Safari accepts everything but hopefully is not a spammer
RewriteCond %{REQUEST_METHOD} POST
RewriteCond %{HTTP_USER_AGENT} !^Mozilla/(.*)
RewriteCond %{HTTP_ACCEPT} ^\*/\*$
RewriteRule (.*) - [F]

Everything was working fine up to 2.3.x, but now Ajax cannot connect to 
the server, if I activate these lines. Suggestions?