amiko alien2 usb problem

hi guys,
I'm looking for help from few days ago my alien 2 (triple tuner) has a problem with the usb input.
following some info that I hope will help someone to locate the problem:
- Normally I use the usb with an external hard disk (with its own power supply) for reading multimedia files
- The hd has always worked so far
- Obviously the hd works perfectly on PCs, laptops , etc ...
- I have tried several USB sticks, reformatted and all with different capacities, the Amiko does not see them (they worked previously)
- Using spark when I plug the usb stick in the video appears for a few seconds the hd icon (top left of the screen), but then I do not see the memory from any menu
- using enigma2 (HDMU image) I see the memory from initialization hd menu but then I get "inizializing storage device error"
- Both spark that enigna2 are updated to the latest release
- The tests described above were made with both the rear and front usb input
anyone has this issue? hope someone could help me, thanks

astra28.2 thank you very much for your suggestion!
just downloaded and installed hdd manager, i selected "mount all at receiver startup" and restarted... now i can see the hdds (i.e. throught mediacenter menu) but not the content, if i try to initialize i have the same problem...