H120 strange USB behaviour

[nofish]

Since some days my Rockboxed h120 shows some strange behaviour, that is it doesn't disconnect fom USB anymore if I unplug (I always use "safe remove" in Win first).

When I power it on without a USB cable connected it also mmediately goes into bootloader USB mode or jumps rapidly between connected/disconnected.
This also happens when I boot to original firmware with Rec. button pressed while booting.

Here comes the strange thing:
It (only) boots in non-USB-mode with the USB cable connected to my PC and the PC is turned OFF. As soon as I pull the USB cable (PC still off) it jumps back to USB mode. (but jumps back to disconnected if I connect the USB cable again).

Same (but even stranger) with my laptop. If the laptop is turned off and USB cable is connected the H120 boots in normal non-USB mode but only if the power supply jack of the laptop isn't connected to a power socket. When I put the Laptop's power supply in a power socket (Laptop still turned off) it jumps back to USB mode (that is I can switch between USB/non USB mode whith just plugging and unplugging the Laptop's power supply).

I'm rather a technical noob but I (wild guess) it could have something to do with earthing/grounding.

Any ideas?
Thanks.

[Llorean]

Please, be careful where you post things. This most certainly isn't a question about how to install, remove, or flash Rockbox.

[nofish]

Sorry, new to the forums.
Overlooked that section.

[Multiplex]

The H100 series have a small board that connects to the HDD and USB, if the connections between that board and the main board fail you get all sorts of strange behaviours with USB and the HDD. Search in this forum and/or mistic river for info.