Here is the log: https://gist.github.com/1274174
It seems to happen around the time the chunk is unloaded that containins the power source/emitter. I have 9 solar panels arranged in the format of a solar flower. Total of 2 bat boxes on the line before hitting my machine room. If you want i can debug it myself using MCP and running it in debug mode from eclipse.
Edit:
And yes I have installed the hotfix.