Solution for "Unable to encrypt" problem with MechCAD AceMoney starting from version greater than 4.20.
1. Open regedit.exe and delete registry key HKEY_CURRENT_USER\Software\Microsoft\Clock\iWeek.
Do not worry, it's not a system key. It belongs only and has been created by AceMoney.
2. For preventing further problems disable internet access for AceMoney.exe, for example by creating new rule in windows firewall.