Script creates the file at /TMP/$filename.txt .The file itself is created by sslstrip. What I can think of is:
1. You don't have sslstrip installed
2. You are NOT running the script as root
3. You don't have a /tmp/ directory pre-created, however I am pretty sure sslstrip can create the directory itself when run as root.

About the font error - it is irrelevant ignore it. It has something to do with xterm and it doesn't affect the way the script works.

EDIT:

This does NOT require arpspoof installed. (actually there isn't a arpspoof package available for maemo at all )