I'm puzzled by the error in the thread title. It popped up today while running a piece of code that was unchanged and had been working before. The error is raised inside a nested loop, so I tried running the loop step by step, i.e. I "manually" declared the first pair of values that is usually declared within the loop and then passed to the function which raises the error. However, running the first iteration of the loop this way no error was raised, and, surprisingly, running the loop in its entirety works fine after having run the first iteration manually.
Any ideas what could cause this behaviour or what this error message is about?
