Hi Mark,
First, thanks for using this group !
I think I never got this issue, and I already ran webiopi for days.
I will take attention in next days.
There is currently no logging facility with the webiopi service
I have to add it but it's not planned yet.
You can try using screen :
$ screen
you will got a new virtual terminal with screen explanation, type enter.
you may have to install it (sudo aptitude install screen)
$ sudo python3 -m webiopi
it will run webiopi foreground with error output on the console
then type CTRL-A then D to detach from the screen and return to your previous terminal
your screen is still running, with webiopi inside, appart from your terminal/ssh
you can reattach the screen :
$ screen -x
then CTRL-A, then D to detach again...
when your webiopi crash, reattach the screen to see webiopi output.
if you don't find any screen, use the uptime command to see if your Pi didn't totally crash.
Eric/trouch