Virtual box USB problems

[Joep L. Blom]

I recently changed my VMware server for VirtualBox and I'm rather 
pleased with it.
However, I have a few problems and maybe more esperienced people can 
help me out.
1. When I type settings for an installed guest OS (Windows XP) I get the 
following error:
___________________
Could not load the Host USB Proxy Service (VERR_FILE_NOT_FOUND). The 
service might be not installed on the host computer.

Result Code:
NS_ERROR_FAILURE (0x00004005)
Component: Host
Interface: IHost {489fb370-c227-4d43-9761-ceb28484fd9f}
Callee: IMachine {1e509de4-d96c-4f44-8b94-860194f710ac}
____________________

When I click OK I can change my settings but USB doesn't work.

2.	I have a .vdmk file (a guest OS made with VMware) which, according to 
the manual could be started. However, I only get a black screen. Guest 
OS is Windows XP

System details:
AMD64 1GB mem, sufficient diskspace. VirtualBox 2.0.0 (not upgraded as I 
read there were some problems with 2.0.2) Ubuntu Hardy 8.04.
Linux 2.6.24-19-generic #1 SMP Wed Aug 20 17:53:40 UTC 2008 x86_64

Does anybody know what the problem is and how to achieve a workaround?
Joep