3Com SuperStack II Manual page 223

You have attempted to upgrade several Switch units in a stack
using TFTP, and one unit fails to upgrade. Take the following steps:
1 Ensure that the unit has:
The IP address 0.0.0.0, or
A valid IP address that is in the same subnet as the TFTP server
2 If the unit has the IP address 0.0.0.0, ensure that the stack has a valid IP
address that is in the same subnet as the TFTP server.
3 Attempt the upgrade again.
Solving Other Problems 223