I just got my Aufenthaltstitel with 'Beschäftigung erlaubt' - as I understand in this way I am not limited to certain employers, however I am planning to do a volunteering project work in Kenya for half a year (without being employed by any companies in Germany during this half a year), will I get in trouble when I come back to Germany beginning next year? My permit is valid till 31 July 2010.
Or maybe if there is any di-registration procedure I need to follow with the foreigner office or any other offices?

Thanks a lot for helping!