PSP - USB Mass Storage incompatibility

[Art]

Hi Guys,
I fitted a new car stereo last fortnight with a USB input designed to play mp3s
off a USB key through the car. which happens to work fine with the supplied 2 Gb USB device.

I also tried playing mp3s from my mobile phone, PSP, and GPS, all in USB mass storage mode,
and found that the PSP was the only device that was not recognized in USB mass storage mode.

I don't expect a magic solution, but was wondering if anyone knows what makes the PSP different?
The reason it's a bummer is that the PSP is the only one of those devices that can be running another
program while in USB mass storage mode, and it's the device I keep most updated with my mp3s.
Art.

[Torch]

You might have tried this, but if you've got a Slim then turn off the USB charging thing. It refused to detect on the front USB of my old PC with USB charging, but worked fine on rear USB. It worked on front USB without charging enabled.