Strange Download Behavior

Normally, after clicking a download link, a dialog box opens to prompt for the download file destination, and then the file is downloaded.

A while ago this behavior reversed on my computer.

Now when I click a download link there’s a long delay (depending on the file size) during which the file is apparently downloading. Then the dialog box opens and the file save immediately.

The behavior reverts to “normal” after a reboot, but it doesn’t stay that way for long.

Any ideas what’s going on?

I’m using WinXP SP-3.

Thanks