Solution for this particular tablet
Ok, this works. The Arnova 8, with android 2.1, has two usb connectors. One for the regular ADB, PC connection, and a second one that can be used as a host. By adding this line of code:
File.WriteString("/sys/bus/platform/drivers/dwc_otg","force_usb_mode","1")
The USB control is transfered to the second port, effectively disconecting the primary USB port and allowing access to the DirRootExternal drive. I can then update my application. On startup, in the create sub, I add this line
File.WriteString("/sys/bus/platform/drivers/dwc_otg","force_usb_mode","0")
which reconnects the primary usb port and my ADB connection is re-established. :sign0060: