As I understand now, lack of chunked encoding support is a real cause of this incompatibility. Chunked encoding is used exactly when content length is unknown beforehand.
As suggested here: http://stackoverflow.com/questions/7721554/httpclient-disabling-chunked-encoding , switching to HTTP 1.0 protocol reliably turns this feature off, and this will ensure compatibility with different legacy/"simple" server implementations.
I will test this and will add corresponding compatibility option to the Social network editor ("Manage Microblogging systems" now).

PS: I don't set content length in AndStatus code. Nowhere. It's done or not by underlying apache.httpclient or java.net libraries.

@moshpirit@quitter.es @andstatus@loadaverage.org @hannes2peer@quitter.se @mmn@social.umeahackerspace.se @lnxw48@fresh.federati.net @knuthollund@quitter.no