It would seem that apt-get is having issues connecting with the repository servers. I suppose it is likely compatibility issues, as mentioned here, however the proposed solution
The httpredir.debian.org mirror is "magic" in that it will load-balance and geo-ip you to transparent increase performance and availability. I would therefore immediately suspect it of causing your problem, or at least be the first thing to rule out.
I would check if you could:
Still reproduce the problem; httpredir.debian.org
will throw out "bad" mirrors from its internal lists so your issue may have been temporary.
Reproduce the problem with a different, non-httpredir.debian.org
mirror. Try something like ftp.de.debian.org
. If it then works with this mirror, do please contact the httpredir.debian.org
maintainer and report the issue to them. They are quite responsive and open to bug reports.