[O] Unable to push to org-mobile

[Dror Atariah]

Today I realized that I cannot execute successfully 'org-mobile-push'. In particular here is the output from '*Messages*':

Creating agendas...

Agenda written to Org file /Users/drorata/Dropbox/MobileOrg/agendas.org

Creating agendas...done

Saving all Org-mode buffers...

(No files need saving)

Saving all Org-mode buffers... done

Copying files...

Writing index file...

org-mobile-create-index-file: Wrong type argument: sequencep, :grouptags

I first step I took was to update the package; now 'org-version' yields 

"Org-mode version 8.2.4 (8.2.4-3-g7fe99a-elpa @ /Users/user/.emacs.d/elpa/org-plus-contrib-20131209/)". However, problem is still here.

Next I don't really know what to do... I have all my emacs' settings in 

https://github.com/drorata/emacs_setup

How can I debug this problem and solve it?