The POSIX error is caused by a bad repo not making a connection with the new jailbreak. Go to Cydia> Manage>sources. Usually the bad repo is the one with the "?" thumbnail next to it. In my case it was an old redsn0w repo that I deleted and corrected the issue immediately.
You've used the term "bad" very loosely. You identified the problem when you pointed out "not making a connection." Others in the thread have done the same. The solution is generally to wait a day or two. See if the problem still exists. Keep in mind, when things like the substrate update hit on a new jailbreak, servers get slammed. The effect is similar to a DOS attack. In these cases, some servers are knocked offline. Some are unable to respond. You'll see errors like these on "good" repos. Deleting the repo is a bit premature.
As r_diddy pointed out, there are several stages to a jailbreak. The first is devs find exploits. The second is Saurik updates the programming backbone for tweak developers. The third is developers update their code to work well with the new iOS and hardware. Typically, the first is released in at least a tethered environment for Saurik and developers. This makes the steps appear seamless to the masses. In this case, the first step was released in advance of the first two. Saurik has worked to get the second step finished. Now, individual tweaks must be updated by their developers. One way to watch this is to read the description in tweaks. Most currently say up to iOS6. Watch for compatibility in the description as you update. Restoring your device doesn't change what external servers or developers are doing.
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