If you use Firefox and notice when it downloads that it takes awhile to do its scanning of the download, you can edit the configuration to disable the scanning and prevent Firefox from "Hanging".

Warning: You should have your own antivirus such as NOD32 if you disable this.

1. In Firefox, type in "about:config" in the address ar.

2. In the search field that shows up, type in: 

               browser.download.manager.scanWhenDone

3. Switch it to False, and restart Firefox.  Now Firefox won't perform its scan of the file, on top of your Antivirus potentially causing a conflict which can cause Firefox to "hang" or lock up.