For several days, I had been unable to download any files using web browsers (IE and Chrome). This included web mail, any file downloads from web pages, etc. On IE the download occurred, but the file simply disappeared after download finished. IE did not give any error messages. It was really annoying. I then tried the same on Chrome. Chrome did the same, the file simply disappeared after downloading. However, it provided a vital clue – it showed an error saying that the file virus check failed, and provided URL to Microsoft Attachment Manager description.
It turned out that the MS Attachment Manager tried to notify anti-virus software (happened to be Trend Micro’s OfficeScan) after downloading. However, this notification somehow failed. Since I don’t have permission to change anything in OfficeScan (it was installed by our IT department) the simplest way is for me to disable this notification because OfficeScan automatically checks any new files any way.
I changed the Windows Registry key from 3 (On) into 1 (Off):