"Failed to Attach the USB Device" (iPhone)

[djuatdelta]

What I'm doing: using iTunes in Windows XP with Guest additions installed on non-open-source edition of Virtualbox.

Usually when I attempt to activate my usb device (iPhone) from within the guest OS, I get the error box telling me "Failed to Attach the USB Device" ...(iPhone)... "busy with a previous request." I have tried unmounting the iPhone from the host OS before activating the USB device, and I have tried removing all fields but the first from the device settings in according with the following advice:
http://forums.virtualbox.org/viewtopic. ... 340#p48131

Anyone else had this problem? Anyone have any suggestions?