I have a customer that bought a RB600 and couldn't connect using the same serial cable he has been using for a long time on previous generation RouterBOARDs. When he switched to a different cable it worked just fine, but on the original cable the terminal would get as far as "Starting Services" and hang. He described it as if the router turned off the serial port once it booted. I updated this router with RouterOS 3.4 and upgraded the firmware to 2.16 before shipping it out. The customer then tried reinstalling the OS with netinstall, but it didn't resolve the issue.

Why would the rollover cable work fine on other RouterBOARDs but not that RB600? Is there some hardware configuration within the board itself that could cause this?

I have had this issue with several MT boards. The solution for me is: Then all works as expected.
-Louis

it has to be a standards compliant cable. like the one described here:
http://www.routerboard.com/pdf/rb600ugA.pdf (page 11)