If AnyDVD pops up a big warning dialog about read errors (suggesting a region-free fimware from rpc1.com, cleaning the DVD, etc), and you're using it inside Virtualbox, then the correct solution is:
Stop the virtual machine. The
Settings icon will become available.
Click it and select
Storage. Select the DVD drive, and a checkbox
Passthrough will appear. Enable that and close the
dialog. When you restart the guest Windows, AnyDVD will be able to
read discs it previously refused to touch. I've a region-2 drive and
can now read the region-4 films I purchased from
2001Video in Brazil. It seems
AnyDVD is suddenly a great deal faster, too.
The other effect of this change is that Windows now has full rights to your DVD drive.