VBox won't restartt after guest machine shutdow.

I am on Windows 10 Pro, build 10240. I have managed to create my 1st VBox by following your tutorial. ( it is VBox v 5.2, because the later oversions won't get installed on my 32-bits )Windows).
It worked fine until I shut down the guest machine (from the VBox guest desktop,). Then, when I tried to power it on again a few minutes later, it wouldn' t restart.
There is a message that I have to disable the USB 3.0 support. and set it for USB 2.0. I did it , but it still won' t start.
Besides, if I remove the USB 3.0 and I reset for USB 2.0, the guest machine won't detect the USB flash drive, which I need because I have to share files/folders from it with the guest machine.
How do I go about it?

Thanks

Ittiandro

Ps : problem solved by disabling USB 3.0 support. It didn't work the first tine, This time it worked. It restarded OK now, but I have to solve two other important issues. I read all that there was to be read ( or almost !), but still I am not out of the woods.
'll open a new thread on those: 1.The VBox doesn't detect my USB Flash drive and 2) How to recover a Drive image file from this USB drive into the VBox guest machine.