Devices did not start up completely after upgrading to Agent 5.5

[Phong Thai_2]

A few months ago before Agents 6.0, 6.1, and 6.2 came out, I upgraded all of managed devices to Compaq Management Agent 5.5. I updated the agent by using the .cmd file (silent install option). Not sure whether this was just a coincidence, or Agent 5.5 did have a problem, but a few days later, some of the servers would not start up. They were stuck at Windows 2000 logo, even the Safe Mode did not work. I ended up restarted the servers from "Last Known Good Configuration". Has anyone experienced similar problem with any of the agent?