Hi,
Thanks for the bug report. I was able to reproduce this problem on my local machine.
Researching it I found this thread in the TinyMCE forums which indicates that the google spellchecker service used by TinyMCE is no longer available. But also on that thread someone posted the changes needed for using a different service that Chrome web browser uses for spellchecking. I've updated our code and it seems to work, hopefully it will keep working in the future but there is no guarantee.
This fix is in our source code repository now and will be in the next release of mojoPortal, for now all I can suggest is use CKeditor instead if you need spellchecking or if you are a developer you could make a build of the latest code from our source code repository.
Best,
Joe