我认为这个版本的 mongoDb 客户端缺少一些默认配置.尝试运行:

I think there is some default config what is missing in this version of mongoDb client. Try to run:

mongo 127.0.0.1:27017

这很奇怪，但后来我遇到了问题消失了:)(所以没有任何参数的简单命令mongo"开始为我再次工作)

It's strange, but then I've experienced the issue went away :) (so the simple command 'mongo' w/o any params started to work again for me)

[Ubuntu Linux 11.10 x64 / MongoDB 2.0.1]