Ok found the culprit.
The file is particles_plugin, line:70
this.webGL_texture = this.runtime.glwrap.loadTexture(this.texture_img, true, this.runtime.linearSampling, this.texture_pixelformat);
This (nasty) bug happens if you switch off WebGL. Noticed it testing on Win8.
Ashley is there a quick fix while waiting for the new version? I was about to publish an update..