Can't Download Parallels Tools Update

I'm currently using Parallels Desktop 4.0.3848.

Whenever I launch the Windows XP guest OS, I get a message saying that Parallels Tools are out of date. I don't know if this is because I'm not running the latest version of Parallels, or if I don't have the most up-to-date Tools for Parallels 4.

Nevertheless, when I try to update the tools, I get an error dialog box that says "Unable to download the installation package."

Is anyone else having the same problem? I can't find a place to download them from Parallels' site, nor a way to get a question like this answered without purchasing support. (IMO, support for an issue such as this should be provided at no charge - I doubt I'll upgrade Parallels again if this is the norm.)

I tried to download the entire installation package again from a link on this knowledgebase page of downloads and the download never started.

Many thanks for any info.