+A command line option that begins with '+' is always treated as a starting line number. The option just after it, though, is always treated as a filename. So if you want to open '+filename.txt' starting on line 1, you should use:
-nano +1 +filename.txt
If a command line option that begins with '+' is followed by at least one more option, the former is always treated as a starting line number and the latter is always treated as a filename. If a command line option that begins with '+' isn't followed by any more options, it's always treated as a filename. Examples:
+To open '+filename.txt' starting on line 1: nano +filename.txt
+ To open '+filename.txt' starting on line 10: nano +10 +filename.txt
+ To open '+filename.txt' starting on line 1 and 'filename.txt' starting on line 10 (if nano has been compiled with multibuffer support): nano +1 +filename.txt +20 filename.txt
Try setting your $TERM variable to 'vt100'. Nano doesn't yet support every term entry under the sun.
Bourne shell users (bash and sh): export TERM=vt100