[Linaro-uefi] No console output with qemu and serial over telnet

I'm seeing some strange behavior when using the "-serial telnet:localhost:5000,server" option for serial output on qemu. I've been been using this for quite some time without problem, but recently I have been seeing a complete lack of output in about 1 in 5 times. At first I thought that it was just hung, but from looking at it with gdb it appears to be booting all the way to the shell. (I get the same backtrace with or without output.) I've tried a couple of different versions of qemu (2.2 and 2.3), and various versions of EDK2 and see the same behavior.

Has anyone else seen something like this?

Roy