<img src="smileys/smiley18.gif" border="0" align="middle" /> I *finally* found the problem.. The noisejs.addon was installed to A:roamaning-something and it prevented even 155 version to start properly.. I never asked anything to be installed there (I keep my C2 files at H-drive).. No wonder It took me some time to find.
Okay yeah, to be more specific:
It appears that some plugins are also put into the hidden folder
c:\users\name\appdata\roaming\construct 2(C being your windows drive and name your username)
resulting in them being duplicate and causing the error apparently. Remove the plugins from that folder and you're good to go again.
I guess it's something that happens or can happen when you install a plugin by dragging the .c2addon file into the C2 window, instead of copying it manually to the plugin folder.
EDIT: Caught the error specific to the perlinjs plugin. I indeed simply forgot to use unique ids for the expressions. <img src="smileys/smiley5.gif" border="0" align="middle" /> For some reason this didn't cause any errors in 158.2 (but it should have!). Sorry for the confusion, was entirely my fault. <img src="smileys/smiley18.gif" border="0" align="middle" />
I'll update the link in the plugin thread with a working version now...