I can remember problems with download.com when avast itself used a stub installer (presumably and not cnet), not downloading the full installation file and that caused lots of problems with on-line installs.
I did some shouting about it as it failed to take account that installing a security application on-line not off-line, means that you either go on-line with no protection (you uninstalled your previous AV) or you went on-line with the protection of your existing AV.
Both of these scenarios bring their own problems, either the possibility of getting infected whilst on-line without protection or problems with failed installs or conflict from the existing AV.
We saw lots of this in the forums, it was some time ago, so perhaps the memories have faded.