Attachment Upload Problem

We have installed Roundcube and love it -- but we are having an attachment problem. We cannot get attachments larger than 2MB to successfully upload to the compose message page. I know what you're thinking -- php.ini -- but both max_upload_filesize and post_max_size are both set to 64M. Apache of course was reloaded as well. The upload_tmp_dir is /tmp (linux system tmp directory, chmod 777 on that dir).

I grepped the entire Roundcube install and there are no ini_set statements that would override the php.ini variables.

This problem has been confirmed on 3 different servers/installations so we're stumped as to what is happening.

Dennis