I'm a computer science student from China, we have to use the vbox for our computer security module. I've googled this problem for about two weeks and tried every possible solutions but no one worked. My teacher also cannot figure out what happened, and I almost wanted to give up and use a VDI instead. Today I looked at the log file and search for discussions here, and I found your post. Thanks god! It works for me
. Thank you very much!!