missing globals?

Are there any circumstances where global variables would become unavailable within a script?
I am using URL Scripting’s upload command and it works just fine. I surrounded it with try/on error routine so I can trap the cancel button on the URL Scripting progress dialog box. If I push that cancel button during an upload it does get trapped by the on error routine as expected. The error routine then tries adds a line to a global gSessionLog. Most of the time but not all I get an error message that the gSessionLog is not defined.
Now gSessionLog is definitely defined because I added to it before calling the upload command. I have also found that my other globals are considered undefined after entering this on error routine. The globals and these routines are all within the main project script.
I am using FaceSpan 3.52, OS 9.2 and AppleScript 1.6 for this project…
Anyone have any idea what would cause this to happen? Has anyone seen this before? Any thoughts would be appreciated.
Thanks, John

A freeze.

As you describe your problem, it is so strange! :!: Could you post the main code you work-with? How do you know “gSessionLog” is/is-not undefined?