Hi rdelvill,
I have tried the command like:
draw -n vline -l -v 5
in Script window followed by pressing ENTER in my Origin 8.6, and it worked.
Probably you put a semicolon(;) at the end of line in Script window, then press ENTER.
Semicolon is OK to be placed to separate multiple commands in a single line,
or when commands are in a script file (*.ogs); but if you enter a single command,
you cannot put a semicolon at the end of the line.
Hope this is the case.
--Hideo Fujii
OriginLab