"Error" when trying to upload via KCW from KMC in KCE

Whenever I try to upload video or image file from my computer with KCW in KMC, the status is set to "Error" very quickly. The video is not uploaded. The apache logs show no access when the "Upload!" button is pressed, so it appears to be a Flash error on the client side rather than a server-side error.

Uploading videos and images from Photobucket works.

What's the best way to debug this?

I'm running KalturaCE (v1.5_linux386) locally on a virtual machine running Debian (v4.0) using XAMPP (v1.7.1). The rest of the management console seems to be working.

Thanks.

Andrew