My Passport randomly switches off when connected to Macbook Pro

Thanks sfo_mac, but I’ve tried erasing it a few times with no success.

WD sent me a double-up cable so I could power it from two USB’s on the Mac, assuming that would give me twice the current capability, but unfortunately they sent a cable that doesn’t fit their own drive! Sigh…

BTW my daughter’s Macbook Air has a rated current of 500mA on its single USB, the same as my 'Pro, and it works fine on hers,  so I’m sure there’s something more subtle wrong than just the current drain. I’ll try it on the old Hp desktop; it might be more useful on that. It’s currently just a paperweight!
Cheers, S/C