grunt doesn't work

[bobo23]

Hi, when i try to run grunt, i always get the same message:

Loading "grunt-karma.js" tasks...ERROR

TypeError: Cannot read property 'prototype' of undefined
Warning: Task "karma:continuous" not found. Use --force to continue.

[denisazevedo]

What's your node version?
I have 7.* and it stopped working too :(

[AshishKumarKarn]

I updated all the dependencies to their latest available version and it started working.