After installing VBox and starting the VM, the host tries to install 'VirtualBox USB' driver but is not succesfull. Changing back to VBox 3.0.6 doesn´t help. While the VM still starts and runs normally, all USB support for the VM is gone.
a Philips Speechmike I, LFH 6274) I tried upgrading VBox to 3.0.8. When I experienced some bad performance of USB-Gear in the guest (i.e. The VM was starting normal and there were no warnings, etc. everything seemed ok after upgrading the host to Win 7. At first (and still with VBox 3.0.6, which I had been running under Vista 64 Bit, due to frequent bluescreens in the guest with VBox 3.0. I´m using a guest with Win 7 RC 32 Bit (before someone asks: I don´t have a 64 Bit RC!). Hardware is a Core 2 Quad Intel CPU (Q8300) with 2,53 GHz and 8 GB RAM. Just upgraded from Vista Ultimate 64 bit (German edition too) where all was ok. I´m running VirtualBox 3.0.8 (same problem with 3.0.6) on a Windows 7 Ultimate 64 it host (German edition!).