Try a complete uninstall of the program.

Looks that iceweasel isn't installed in a path that can be found via the path environment variable.
Try: locate iceweasel or check your software (package) installer to find the location of the program.

Start iceweasel via a shell script:

#!/bin/sh

cd <path to iceweasel>
./iceweasel

Thank you for your suggestion. I like it, however, I have already uninstalled and re-installed Iceweasel. Now it works. If I had not already done that, I would have tried your solution.

Best wishes,

Chas