Object reference not set to an instance of an object.

系统登录偶尔出现的问题
一个系统登录时偶尔会出现以下错误，导致登录不正确，请问各位是什么原因？有没有办法解决？
先谢谢各位啦！！！

程序出错，错误信息：Object reference not set to an instance of an object.

程序出错，错误信息：A transport-level error has occurred when sending the request to the server. (provider: TCP Provider, error: 0 - An existing connection was forcibly closed by the remote host.)

链接：https://bbs.bccn.net/thread-305698-1-1.html