Using the ubuntu-vivid kernel branch, 3.13.0-18.38 works OK.
That branch has no tag Ubuntu-3.13.0.20.24 or Ubuntu-3.13.0-20.24. The closest tags I see are Ubuntu-3.13.0-19.40 and Ubuntu-3.13.0-20.41. I'll try 3.13.0-19.40 next.
Using the ubuntu-vivid kernel branch, 3.13.0-18.38 works OK.
That branch has no tag Ubuntu-3.13.0.20.24 or Ubuntu- 3.13.0- 20.24. The closest tags I see are Ubuntu-3.13.0-19.40 and Ubuntu- 3.13.0- 20.41. I'll try 3.13.0-19.40 next.