Moving Table row isn't working in FF

Hi friends :),

I’m attaching the files. Please go though the file
It is a table row moving script.
The script is working fine in IE. But i got stuck with FF.

Firefox isn’t moving the row in one click. I have to click twice or thrice to move the row.

I have put an alert to test the content of variable and it shows undefine in the first click. When i click again it shows the tr content.

Why this happens?
Could you please help me?

Thanks in advance