One of our customers (Andy Little) ran into this when he was VPN’ing into his corporate network. Disconnecting the VPN worked for him. Mysterious!
Another customer (Steve Wilkinson) found that this error also occurs if you have an invalid proxy set up in your Windows Internet Options dialog—if you’re using Firefox to browse the web, you wouldn’t realize you have an invalid proxy as it has its own proxy settings, but it seems that the Adobe Air downloader uses the Internet Explorer HTTP settings, not the Firefox ones.
Keywords: Installation Error