This is really weird. I'm using dozens of such jumping commands and it works perfectly.
What shell are you using? Bash? Maybe try this:
#!/bin/sh if [ $TM_COLUMN_NUMBER -eq 1 ]; then open "txmt://open?line=1" else open "txmt://open?line=$TM_LINE_NUMBER&column=1" fi
Do you have BBedit installed?
What happens if you execute :
open "txmt://open?line=10&column=2"
in the Terminal?
--Hans