I've had download problems with Safari and Firefox like this before. I received an email from Google about the beta release of Chrome so I went to the site and clicked the link to download it. It opens the link in the same window, runs for a while, and then quits and does nothing. Usually Safari then freezes and I have to force quit and restart it. Same exact problem when I tried the link in Firefox. I have enabled Java scripts and I'm not running any 3rd party apps. I have OSX 10.6 and Safari 4.0.
I have the same problem when I try to download the latest versions of Abode shockwave.

Any ideas as to what's going on and how to fix it?