I've got an XP guest, running on a XP or Win7 host. I wanted to run OperaUSB from the Host drive, so I setup the folder it's in (D:\Portable Apps) as a Vbox Shared Folder and this is Automounted to E: on the guest.
The problem is, if I run OperaUSB from there it loads fine and starts opening my saved tabs but then the network connection seems to stop working (windows doesn't say that it has, but there's no data transfer) and everything grinds to a halt and at this point even IE or ping don't work. If I copy the OperaUSB folder to the guest C: drive and run it from there however, it works fine.
In the NIC (Intel Pro/1000 MT) properties on the guest, I've just got QoS Packet Scheduler and TCP/IP enabled.