Synaptic List saves as zero bytes

[Dave M G]

Ubuntu users,

I'm trying to save my current list of installed packages, so I can 
restore my system as easily as possible if I need to recover from backup.

However, no matter what I do, the file that gets created is always 
completely empty, and is zero bytes.

I've searched Google, and the instructions are pretty simple. Select the 
packages, then save the list.

That isn't working, though, so what else should I try?

Thank you for any advice.

-- 
Dave M G