This is some information that can arm you with some knowledge to assist in debugging of your WML if a gateway is having a problem encoding it.
The trick is to increase the debugging level of your local server simulator. There is some overhead by doing this, so if you have an underpowered machine with in inadequate amount of ram, you might not want to do this on a full-time basis.
To increase the logging of your server sim...
1) Quit Toolkit 3.0 if it's running.
2) Locate the directory where you've installed your Toolkit.
3) Find the directory called "WapServer"
For most of us this, this will be C:\Program Files\Nokia\WAP_Toolkit\ServerSimulator
4) open the "config" folder and locate a file named "Logging.config". Delete the file (or rename it if you're not comfortable with deleting)
5) Go back up one directory and locate the directory named "config.default".
6) Locate the file "Logging.config" and open it for editing in a text editor.
the file contains..
#Configuration of Logging
#Fri Apr 05 08:24:09 EST 2002
Take notice that some of the line items have single digit numeric settings.
7) Change all the settings that are single digits to the number 7.
8) Save the file, exit your text editor and then start the Toolkit.
Of course, this will only help for WML and WMLS debugging. It will not assist in the debugging of any other mark-up languages.