It is like Greydon writes, the problem occurs when you:
1. Build from source on linux
2. Download the chains from scratch
It is a known problem in earlier version of Bitcoin, and the Bitcoin internal version running in Credits it 0.9.1. It probably have something to do with the openssl version.
I'll create a fix for this issue by disabling the validation of the offending blocks in the Bitcoin chain. I'll post here as soon as it's done, probably in a couple of days.
There are three (four) ways around the problem:
1. Use one of the official Linux releases
2. Use the torrent provided here: http://credits-currency.org/viewtopic.php?f=18&t=517
3. Build a release version by ourself by following the instructions for creating releases: https://github.com/credits-currency/credits/blob/master/doc/release-process.md
4. Wait until i can add exceptions to the code base to get around the problem. This will take a couple of days.
Building a releases version is done by building it on a VirtualBox virtual Linux instance. It can be done on any operating system that supports VirtualBox.