[Orgmode] debug agenda-buffer deadlines

[Christopher Kuettner]

yesterday I added some deadlines to my sole agenda-file.  today, when 
invoking *Agenda* with C-c a a I get following message:

org-agenda-get-deadlines: Wrong type argument: number-or-marker-p, nil

The *Agenda* is shown but when I want to switch day/week I get:

org-agenda-check-type: Not allowed in nil-type agenda buffers

Invoking the *Agenda* with C-c a L gives me:

byte-code: Cannot restrict agenda to current buffer

Regards,
 Christopher