May I know what is the exact error message we receive during download ?
What is the computer's operating system ?
How it is currently connected to internet ?
Do you have any other security software installed ?
It says Your McAfee software download cannot continue because either there is a problem with your internet connection or the McAfee download server is unavailable. To fix this, make sure your PC is connected to the internet or wait a few moments for the server to become available, then try again.
Please check the following before proceeding with the download;
Check and delete if you find any other security software in add/remove program or their files & folders in C:/program files & common files.
Run the Mcpreinstall tool from here
Restart the computer in safe mode with networking (Press F8 while the computer restarts)
Try installing the programs and let me know if you come across any issues.
Are you using Verizon Fios? I am on Fios and was having a problem with the downloads until McAfee gave me an alternate IP address to go to (Had to update the Host file, which does get reset by the operating system from time to time, so always recheck if you need to reload again). It seems that there was something specific in the datastream that the router didn't like and then it wouldn't access the internet (for any computer plugged into it) and I had to shut the router off and reset it.