problem with dotNet.System_IO.File.WriteAllText

Hi folks,

I'm using method dotNet.System_IO.File.WriteAllText to write some data to CSV. The thing is it started to fail with below JavaScript error...

It definitely worked before. But I'm not quite sure, when it started to fail, because it's in a part of code, which is used only occasionally (to create new ref. data). 

Of course, I'm aware that I can use aqFile.WriteToTextFile function. But it creates a file with BOM, which I need to avoid. Therefore, I was using above dotNet method (as suggested here). Any idea what's wrong with my code? Thanks.