Works fine here too (4.50).

Is this a local filesystem or a networked one? If networked, what OS is the file server?

Is your anti-virus sw causing the problem?

Have you tried just isolating the Exist() function in a script on it's own of just two or three lines to ensure that it's not something else in the full script which is causing the problem?

What is the context of the funky character? Where do you see it? Is it just a feature of the display rather than the Exist() function?