@tony bombata said:

interestingly, if you pin a file to sketchup 2014, and launch from the taskbar jumplist, it will open without errors - dont know if that helps

Thank you! It works!
I think it may be linked with SU current "Working Directory".
I tested some random folders. If current working directory is on other drive than SU installed(maybe it should be only C:) plugin crashes.
I have profile folders on D:. When I'm starting SU with desktop shortcut SU's working dir sets to D:\Profile\Desktop. When starting from pinned shortcut - C:\Windows\System32\

jiminy-billy-bob, you are using relative paths in source. Maybe ruby engine tries load file using current working directory and only it's drive(D: in my case)
Maybe there is way to set up current working dir to system drive or any MS API to find system drive and try load required libraries with that path?
Or is this SU bug and about this should think SU developers?

I think any can repeat this bug in Windows just changing "Working dir" in shortcut to any folder on any another than system drive.
Is there bugtracker?)

After reinstalling SU Make, cleaning directory in %AppData% I have same error...

I still have same error. Opening new 2014 file...
Your advice was helpful with my PC, but on laptop it does'nt work... I will try reinstall SU.

@jiminy-billy-bob said:

Are you using the last version of Layers Panel? Is this a fresh install?

Yes, latest version 1.0.0.
Reproduced on other PC. I removed SU2013, cleaned up folders and installed SU2014(Make) and plugin.
I get this error just opening SU.

This is really weird: after saving my old 2013 file and relaunch SU - plugin is working.
Last opened file affects on plugin loading?

This plugin doesn't work on my laptop.
After installing it shows, works. But after restarting SU it crashes.
Stack:

Error Loading File C;/Users/vremennyi/AppData/Roaming/SketchUp/SketchUp 2014/SketchUp/Plugins/jbb_layers_panel/layers_panel.rb
Error; #<LoadError; cannot load such file -- Win32API>
C;/Users/vremennyi/AppData/Roaming/SketchUp/SketchUp 2014/SketchUp/Plugins/jbb_layers_panel/layers_panel.rb;19;in `require'
...

I'm using Win 8.1 x64.