So this is now a different failure mode to the one which you originally
reported (pygrub failed)?
What does your guest config look like now that you have resolved the
pygrub issue?
Can you provide a full log of the failing boot with a vif enabled to the
point of the hang?
Are your hotplug scripts set up properly?
What does "brctl show" say while the guest is running (with the vif
enabled)?
What does "xenstore-ls -fp" show while the guest is sat waiting?
I can only find oi-dev-151a-x86.iso and oi-dev-151a-text-x86.iso here
(and the usb stick equivalents).