[pups] Problems booting PDP11/40 using vtserver

Hi there, I have my PDP11/40 connected to a MicroVAX 2 (running NetBSD/vax 1.5.2) via serial line and want to boot a 2.9BSD or 2.11BSD using the vtserver software. When I toggle in vtserver's boot code, the first file is being loaded correctly by the PDP. Then, following the instructions in vtserver documentation, the serial line should be used as a serial console - and some text should appear! And this is the problem: I don't get any output. When manually sending characters from the PDP, there is no problem. I've set the serial line characteristics to: Speed 2400, Character Size 8, Modem Control enabled, and RTS/CTS flow control disabled. (I've changed these characteristics in many ways with stty, but still no success...) Using a break-out-box, I switched RTS/CTS and DTR/CTS flow control on and off, forced the CTS line to be on, etc., but it still didn't work. After successfully loading the bootloader via vtserver, the PDP's CPU goes into an endless loop. So, my question: Does anybody know what's going wrong here? Thanks in advance - Michi