That is definitely a new one to me and just when I thought I knew of all the quirks with Frontpage.... I can only imagine over time it slowly degrading to the point of usability though I can't say when that will be, I can say that MS has dropped support for that product and if I were to guess why, it is because of all the problems with the old proprietary extensions.

MS Frontpage was EOL'd in December 2006. I am sorry I have never heard of that, perhaps it is a setting in the My Network Places that has been configured to automatically launch the web when connecting to the Internet? That is my best guess.