Hi,
I downloaded the Kali 2018.1 OVA using the torrent download.
The checksum looks fine:
$ sha256sum kali-linux-2018.1-vbox-amd64.ova
fc8c720284eb5d3e0145b9634c76ef2b7c47d8f46ced683f29 62d8a4f55785ed kali-linux-2018.1-vbox-amd64.ova

(Which matches the checksum on the download page).

I tried loading on my machine running Ubuntu 16.04.3 LTS 64-bit, VirtualBox 5.0.40_Ubuntur115130.

And I get the error message:
Failed to import appliance

Details
- Seeking within the archive failed
(VERR_TAR_UNEXPECTED_EOS)

Result Code: BOX_E_IPRT_ERRO
(0x80BB0005)
Component: ApplianceWrap
Interface: IAppliance
{8398f026-4add-4474-5bc3-2f9214023e}

virtualbox_kali_error.jpg

Any suggestions? Is the OVA file broken?

Thanks!