Before you proceed to conda update --all
command, first update conda with conda update conda
command if you haven't update it for a long time. It happent to me (Python 2.7.13 on Anaconda 64 bits).
the Conda Package Manager is almost ready for beta testing, but it will not be fully integrated until the release of Spyder 2.4 (https://github.com/spyder-ide/spyder/wiki/Roadmap). As soon as we have it ready for testing we will post something on the mailing list (https://groups.google.com/forum/#!forum/spyderlib). Be sure to subscribe
Cheers!
# list packages that can be updated
conda search --outdated
# update all packages prompted(by asking the user yes/no)
conda update --all
# update all packages unprompted
conda update --all -y
Source: Stackoverflow.com