Parallels 5 problems with serial port mapped to socket

(I've submitted this as trouble ticket 1072790)

I'm kernel debugging between VM's using Windbg. The port on both sides is mapped to /tmp/pkdebug. The debugging host is set as client, the target is server. My boot flags on both ends are set to "devices.serial.pipe_WinDBG_Hack=1".

This is Parallels 5 build 9376 and OS X 10.6.5. I saw the same problems with 10.6.4.

There are two issues:

1. When enabling the serial port I get the message:

"Unable to connect the serial port 1. The connection status for this device is set to Disconnected. The socket required by the serial port 1 is used by another processes or you do not have the permission to access it. The virtual machine will continue running, but the serial port will be disconnected."

Sometimes an enabled port will stop working when I reboot the VM. If I try repeatedly to enable the port, it might finally succeed. Sometimes I have to suspend and resume the VM. Today, however, I can't get any port to enable from any VM.

I have the same problem with Win7 32, Win7 64, and XP SP3 VM's.

My low level Mac knowledge is limited, but I see with fs_usage that the OS is returning errno 13 when prl_vm_app tries to connect to the socket. I've verified with lsof that no other process has the socket open. I've verified that the owner of the socket file is my user, in group wheel. Prl_vm_app runs under that same user. I've also seen that if I delete the socket file, it is not recreated when I attempt to connect to the socket.

I have run repair disk permissions in OS X's Disk Utility.

2. Even when both VM's can open the serial port, the debugger frequently cannot connect. Sometimes it connects immediately, other times only late in the boot cycle, after Explorer has started. Breaking in repeatedly from Windbg and cycling the kernel connection do not help.

Thanks for any help,
Gary