W Digital drive not vissible

[Klipspringer]

From time to time ; my "WD my story 1(or2)" harddrive disappears and It take a hour or so to get back; I can't see it in the finder ; its connected via firewire and the 2nd WDigital drive is daisy chained through the first one so there isn't a problem with the wires as the 2nd drive are visible.

I also used the usb port and still not vissible(apart from being grayed out in disk utility)

I used disk utility and the drive is visible but grayed out; I did disk verify ; and after +-4 minutes it tells me that verification was successful (in green letters) the option to check disk permiSsions is not available

you can hear the disk running/spinning (normal sound) but its not available to be used

I tried option+ P on start up to reset pram (for what its worth ) but I can't see that it actually working/resetting( it doesn't do a restart)


Any ideas that what it could cause the drive disappearing?

Thanks

Running mountain lion; but it used to happen on snow leopard as well ; but I usually got it going again by fiddling much faster the previous times.

 

[Grant]

have you tried connecting it on its own.
have you tried connecting via usb

i presume these are 3.5" drives powered by external sources, not 2.5" drives that rely on power delivered through firewire

 

[Klipspringer]

I have tried it on its own and through usb ; it has its own power supply yes; and I can see the light going on and running 'up and down' the front panel; and it does the normal sounds it used to do; I can just not 'mount' it