This may or may not help, but I've been fighting a boot lockup and USB dropouts on my A3K ever since I got my DENEB a few years ago. Those errors are very familiar to me.
I finally resolved the lockup and errors this week by removing the PsdStackloader line from the User-Startup; this was saved in the ROM of the DENEB as well so I wondered why it was running from both places and took a chance. It paid off. Since I removed the line, I haven't had a single boot lockup. I'm thinking there is something that gets confused when this command tries to re-do what was done from the ROM call.
The only downside now is that when I warm boot, I lose my USB network dongle. I guess I now know why it was in both the ROM and User-Startup now. But a power cycle to it in Trident brings it back and to me that's a lot easier to live with than a boot lockup that happens 9 out of 10 times.
I'm going to try to fiddle with the PsdStackloader in User-startup when I get time to see if I can correct the locks without having to remove the line for good but at least I'm in a better place now.
I don't know if the ROM on the Rapidroad has the PsdStackloader in it but maybe you'll get lucky and this is the trick you're looking for...
