grunt "Error: Cannot find module '../time/convert' (only on windows)

Setup a new angular project under linux. Committed it to git and cloned it to windows. Using bower and npm, I managed to get everything loaded, except, I have this one error (only on windows)

A recursive grep for ../time/convert in the project shows me:

./node_modules/grunt-contrib-imagemin/node_modules/gifsicle/node_modules/bin-wrapper/node_modules/mout/date/diff.js:var convert = require('../time/convert');
./node_modules/grunt-contrib-imagemin/node_modules/gifsicle/node_modules/bin-wrapper/node_modules/mout/src/date/diff.js:define(['./totalDaysInMonth', './totalDaysInYear', '../time/convert'], function(totalDaysInMonth, totalDaysInYear, convert){
./node_modules/grunt-contrib-imagemin/node_modules/optipng-bin/node_modules/bin-wrapper/node_modules/mout/date/diff.js:var convert = require('../time/convert');
./node_modules/grunt-contrib-imagemin/node_modules/pngquant-bin/node_modules/bin-wrapper/node_modules/mout/date/diff.js:var convert = require('../time/convert');
./node_modules/grunt-contrib-imagemin/node_modules/pngquant-bin/node_modules/bin-wrapper/node_modules/mout/src/date/diff.js:define(['./totalDaysInMonth', './totalDaysInYear', '../time/conve

but ls -l shows:

$ ls ./node_modules/grunt-contrib-imagemin/node_modules/gifsicle/node_modules/bin-wrapper/node_modules/mout/time
convert.js  now.js  parseMs.js  toTimeString.js

Which says that convert.js is actually there. Being new to grunt and angular, I'm puzzled where this could be coming from and how to troubleshoot it.

After this I end up getting stuck here:

Running "karma:unit" (karma) task
INFO [karma]: Karma v0.10.4 server started at http://localhost:8080/
INFO [launcher]: Starting browser Chrome
WARN [watcher]: Pattern ".../test/mock/**/*.js" does not match any file
WARN [launcher]: Chrome have not captured in 60000 ms, killing.
INFO [launcher]: Trying to start Chrome again.
WARN [launcher]: Chrome have not captured in 60000 ms, killing.
INFO [launcher]: Trying to start Chrome again.

Wondering if angular work using grunt is just not possible on Windows....