If Motorola XOOM is connected with USB devices and working as USB Host mode, you will not be able to have adb shell work on PC. The only USB connection is used for other purpose. Here is a tip to have a console with root even the USB connection is used for USB device.
- Motorola XOOM is rooted
- Push a busybox to Motorola XOOM, make it executable
- Connect Motorola XOOM with PC, in a PC cmd window, adb shell to the device, the shell must be a root shell.
- Start telnetd: busybox telnetd -l /system/bin/sh
- Download a telnet APP for Motorola XOOM, e.g. BlowTorch. Launch telnet client (BlowTorch), telnet to device, a root console is served.