I am running Windows 7 x64 (german) with Poser Pro 2014 (build 10.0.2.25578) and, as mentioned above, Octane 1.51 and Octane for Poser plugin 1.50 (build from March 25th, 2014).Traceback (most recent call last):
File "C:\Program Files\Smith Micro\Poser Pro 2014\Runtime\Python\addons\OctaneRender for Poser\Node.py", line 1374, in <lambda>
File "C:\Program Files\Smith Micro\Poser Pro 2014\Runtime\Python\addons\OctaneRender for Poser\SetupForm.py", line 1765, in comboBoxNodeType_SelectedIndexChanged
File "C:\Program Files\Smith Micro\Poser Pro 2014\Runtime\Python\addons\OctaneRender for Poser\Node.py", line 452, in ChangeNodeType
File "C:\Program Files\Smith Micro\Poser Pro 2014\Runtime\Python\addons\OctaneRender for Poser\Node.py", line 389, in ReplaceNode
WindowsError: exception: access violation reading 0xFFFFFFFFFFFFFFFF
I loaded a render-ready scene which had no Octane info in it yet (though the same happens with a completely new scene, so just mentioning it for completeness) and then went on to set the plugin up. When I tried switching from "Daylight" to "Texture Environment", I got the above error. Though it also spews exactly the same when I try to switch anything in the plugin that has a drop-down menu.
One thing that struck me as odd is that I have PPro 2014 installed under "L:\Poser Pro 2014", not on the C: drive (and heavens forbid not in the "Program Files" directory) as mentioned in the error.
Searching for defaultrendertarget.por as suggested yielded no results, neither via the Windows search nor the manual search via Speed Commander. It seems that the file does not exist on my machine.
I then de-installed both Octane and the plugin via the Windows Programs and Applications window, rebooted and re-installed both, cleared out all Octane related files from my "AppData" directories as well as from the Poser Temp folders (where it stores the logs, for example) and then tried again.
Sadly, I got the exact same error again.

I have included the log file as an attachment, if that helps in any way.
Oh, and going back to my earlier Octane versions (1.20/1.20a respectively) works for me without any errors, so I suspect the error is somehwere in the new versions. But where, that is the providence of men smarter than me.

Cheers and best regards,
SpiritWolf448