As it turns out, the issue had something to do w/ encoding and not w/ that path at all. Not sure why it exhibited the way it did, but there we go.
Thank you for your assistance, board and @Jorropo .
EDIT: I am not specifying Abspath: My body looks something like this:
----------------------------a_separator
Content-Disposition: form-data; name="file"; filename="pxArt.png"
Content-Type: image/png
<file data>----------------------------a_separator--