If thats where you got the error, check the vmdk filename/path.
I use a completely different approach to virtualbox. I make some adjustments to the ova to allow it to import directly. I've posted about that in some other threads on vbox, but I can post an 832 version that helps.
If this post resolved your issue, help others by selecting ACCEPT AS SOLUTION or adding a KUDO.
I've gone through this thread and tried/checked all of the recommended settings, but am still receiving a /cfcard panic upon booting the 8.3.2 cDOT simulator in VirtualBox 5.0.26. Has anyone else been able to get this setup working from the OVA that's provided and if so would you mind sharing the steps taken? Thank you in advance.