OK Problem solved:
Found in another thread (can't remember where...) -
Add a DWORD "Secure" with value 0 to HKCU-Software-Microsoft-Activesync-Partners-{GUID}
GUID is one of the keys that represent the computers you want to sync with. You have to find the one for your server.
After adding the DWORD: disable SSL in the "Configure Server" in activesync. Sync once (error of course). Enable SSL back and it work.
This change disables the certificate check. Works until there will be a new fix...