Tools won't install

I was running Parallels 4.0.3846 and XP without problems. I then upgraded to OS X 10.5.8 Leopard, NOT snow leopard) by archive and install. Parallels wouldn't start up. looking at the forums it appears that "archive and install" results in problems with parallels.

so, I downloaded 4.0.3846 from the website and reinstalled parallels. parallels now starts and windows runs but when I try to install/reinstall tools I get the following message: "unable to download the installation package".

how do I resolve this?
thanks,
Pete

OS X 10.5.8
macbook pro 3 gb ram