Debugging shell file failure (vimrun on Windows)

I'm trying to run a script on the selection. This is on Windows 7 (64-bit).

Basically, I'm selecting and area of text, then running :'<,'>!myscript.py

The command returns with no output and a message "the command returned exit status 1". There is no information as to what went wrong, and when I try the same command from a command prompt, it works fine.

I suspect there is something odd in either the quoting that is going on, or the environment used in the cmd.exe shell that is being executed by vimrun, but I don't know how I can find out.

Can anyone suggest a way of debugging what exactly vim thinks it is running when this command fails?

Thanks,
Paul.

--
--
You received this message from the "vim_use" maillist.
Do not top-post! Type your reply below the text you are replying to.
For more information, visit http://www.vim.org/maillist.php

---
You received this message because you are subscribed to the Google Groups "vim_use" group.
To unsubscribe from this group and stop receiving emails from it, send an email to vim_use+unsubscribe@googlegroups.com.
For more options, visit https://groups.google.com/groups/opt_out.