Firefox 3.5 uses SQLite. I don’t know when it switched from downloads.rdf

Anyway type About:config in address  bar

put browser.download in the filter

This means items stay in window till you press Clear:

browser.download.manager.retention  1

This stops an automatic virus scan which is buggy:

browser.download.manager.scanWhenDone false

That fixed my Download manager Window

Disable Sites seeing your history?

In address bar About:config

layout.css.visited_links_enabled = False