uploading files with mod_rewrite enabled

I have a weird problem. I'm using Uploadify to let users upload their Avatar. My .htaccess file looks like this:

<IfModule mod_rewrite.c>
    Options +FollowSymLinks
    Options +Indexes
    RewriteEngine On
    RewriteBase /
    RewriteRule ^profile/([^/]*)$ /mysite/profile.php?a=$1 [L]
    RewriteRule ^([^\.]+)$ /mysite/$1.php [NC,L]

</IfModule>

When I visit my page like this: http://localhost/mysite/profile.php?a=avatar the avatar is uploaded fine.

However, when I try this: http://localhost/mysite/profile/avatar I keep getting a HTTP error and nothing happens.

So I think this has something to do with开发者_运维问答 the Mod_rewrite rules.

Anyone ever had the same problem before?

Thanks in advance.