With the release of version 52 we introduced a bug which causes our client to crash if the Windows firewall is disabled. To resolve this, please enable the Windows firewall.
We also introduced a bug which might result in Windows users that have another system language than English not being able to connect. To resolve this we urge users experiencing this problem to downgrade to version 51 of our client software.
We're of course sorry about these regressions and will be hard at work releasing a new version that fixes these problems shortly. To limit the problems we've also reverted the download link for Windows on our website to version 51.