Occasionally, removing unnecessary Win95 networking components will fix things. This is one of the toughest problems to diagnose because there are so many potential causes. Any irregularity in the copper lines or switches or even external factors like nearby lightning can cause noise. Modems are designed to filter out noise but this is not foolproof with even the highest quality analog modems. Occasional dropped connections will happen.
Frequent disconnections are a sign of other trouble though.
However, emergency situations may require us to reboot systems or replace equipment. This may cause temporary periods of downtime. This is so you'll get logged out properly even if you go away from the computer without remembering to disconnect. This would not happen in the middle of a download, chat, or Web browsing, but could happen if you are composing or reading a long mail message or post. Another reason would be if someone else is using your account at the same time as you.