Well then, it likely has nothing to do with your plugin.
Exactly.
It could be a file access clash.
I was thinking along those lines - i played around with moving zorro to different folders, also on another machine/ other operating system. Zorro normally behaves very good with multiple instances. But i didn't run another, no. Honestly i ran out of ideas for now.
I run zorro on a parallels virtual machine(Windows 8) on osx, and an ec2 instance. There was never a filesystem problem before.
I reinstalled Zorro clean. Tried a few different scripts, even Workshop Scripts, fumbled around with assetlists and accountlists.
Windows error 22 indicates a disabled device, or outdated driver.
