NPM list giving 'npm ERR! invalid' output

I am new to nodejs and i had just installed bower module globally. Ever since then, npm list command gives the following output which I searched for on the web but couldn't find any help :

**npm ERR! invalid: chalk@0.5.1 /usr/local/lib/node_modules/bower/node_modules/chalk  
npm ERR! invalid: ansi-regex@0.2.1 /usr/local/lib/node_modules/bower/node_modules/chalk/node_modules/has-ansi/node_modules/ansi-regex  
npm ERR! invalid: configstore@0.3.1 /usr/local/lib/node_modules/bower/node_modules/update-notifier/node_modules/configstore  
npm ERR! invalid: object-assign@0.3.1 /usr/local/lib/node_modules/bower/node_modules/update-notifier/node_modules/latest-version/node_modules/package-json/node_modules/got/node_modules/object-assign  
npm ERR! invalid: registry-url@0.1.1 /usr/local/lib/node_modules/bower/node_modules/update-notifier/node_modules/latest-version/node_modules/package-json/node_modules/registry-url  
npm ERR! invalid: strip-ansi@0.2.2 /usr/local/lib/node_modules/bower/node_modules/update-notifier/node_modules/string-length/node_modules/strip-ansi  
npm ERR! not ok code 0**

The rest of the output is normal and lists the installed modules. Can anyone explain what's going on?

It means that something depends on, for example, "async":"0.9.3" but when they do require("async"), npm thinks that they'll get some other version. And also check that the dependencies and their versions listed in your package.json file are available.

If everything is right then you can solve this problem by npm-update and then npm install.