This looks to me like you are using an environment variable within your script - cron does not set up any kind of environment.
Another possibility is that you may not be explicitly referring to ksh in the #! path at the top of your script, cron executes everything in sh.
That warning of an ambiguous redirect is probably the crux of the issue, but your commandline isn't doing any redirection.

Can you try posting your crontab line, and perhaps your script too?