I've sporadically had problems for yonks with "Bad Header Line" errors when "apt-get update" executes, and I seem to have located the fix.
apt is a very demanding HTTP client, and it's not at all tolerant of slightly iffy proxies - like, say, the transparent ones my ISP has. That run on port 80. Marvellous.
The fix? Bin HTTP and use an FTP repository instead.
And no, I still haven't got Jabber fixed. I'm still experiencing the problem where Erlang won't locate its crypto_drv module. Given that it does this when I use the Erlang I've downloaded and compiled myself, I'm all out of ideas. Erlang experts, anyone?