Quote - The AV Software has Scanned the File on Download, which will normally corrupt Compressed Files. In these cases you will need to Redownload, after turning off your Scan During Download. Check your permissions for Domains. Some programs you have to give permission for both, Downloads and Access. Access alone will not guarantee Downloads. I recommend turning on Prompts for Actions, so you can see what your AV/Internet Security is doing when accessing a site. You will figure out real quick which Prompts you do not need to see everytime and whether you can allow or exclude those options. Ones that you may want to allow from one site but not another, you  should keep as a Prompt.

This is very sage advice :)