Problem uploading video

Hello, everyone!

I’m a newcomer to WordPress and I’m using the service specifically for video blogging. I uploaded my first video (quicktime movie) on the “Write a new post” page with no problems. But now when I try to add additional videos, the “upload files” box disappears, and this text pops up:

This script was not meant to be called directly.

Any ideas on how to go about fixing this? Thanks very much for your help and patience!