It can take some time to recognise an external USB HDD or HDD camcorder but this may be related to the amount of files on the HDD it has to process?
This would be my guess. On my Panasonic TV, when I plug in a USB stick it initially takes a while to read and find the correct file formats. Time taken depending on how many files are on the device.
But once read you can then switch between different media files quickly. As an example if you were originally looking through movie files on the device, when you then change to look at pictures it loads instantly as if it has indexed all files and file types on the device on the first loading.
As said this is on a tv via usb input, so if you get a chance to test it on the 720EB it'd be much apprecited as I'm currently considering buying one.
I'd love it if you could specifically test:
1. An HDD/USB device with many different media types and files on (MKV, mp4, divX, Xvid, flv, jpg, tif, gif, bmp, , mp3's, flak, wav, ac3, etc)
2. Once loaded switch between media types (Video, music and pics)
3. A usb device with only a single MKV/mp4 file on it.
Using these two we can soon see if it does actually load and play the file formats and then see if indeed it is simply taking time due to many files on the device it's reading in addition to if I'm correct thinking it loads and indexes all files on a device at once, to save time and negate waiting for loading each single media type.