js context

Yesterday Chris encounter an problem which appears only in FF3 (what's a garbage!), when visibility shows up a table-table it appears dead and does not respond to any user action.
Digging out I found the problem was in executing a text stored script in the window context.
I have to execute script using the eval.call() method. But a variable created inside that text script can not be accessed in the global scope, only as window's data member.
Alvin pointed me to this http://piecesofrakesh.blogspot.com/2008/10/understanding-eval-scope-spoiler-its.html
It seems this ground is very unsteady and I should watch out.