Rob,
Thanks for the logs. I found the problem. The "Reverse sign of angle" setting in the brain got broken several releases ago when we refactored the brain UI. For those of us who had already had the correct setting and did not need to change the setting, the problem had no effect and went undetected.
Here's a fixed version to try: http://openphdguiding.org/phd2-2.6.1dev11test1.exe
It's just the PHD2 executable, so you'll need to save it as phd2.exe in your phd2 install folder, ordinarily C:\Program Files (x86)\PHDGuiding2\
If you could confirm that it fixes the problem, then I'll release it as 2.6.1dev12.
Andy