Does zencart support a real bugtracker? It doesn't appear the one at SourceForge is used.

At any rate: There is a bug in includes/modules/pages/product_info/jscript_textarea_counter.js that causes text already entered to be replaced if max chars is exceeded. Here is the offending line:

Code:
10         field.value = field.value.substring(0, excesschars);
The correct code should be:

Code:
10         field.value = field.value.substring(0, realchars.length);
Version 1.3.8a