First of all let me say that sending emails works. Never had problems with it. It's configured ok.

This morning I saw about 20-30 logged errors in NopCommerce, related to emails not being sent. Here it is:

Log type:  MailError  
Severity:  11  
Message:  Error sending e-mail. The parameter is incorrect.  
Exception:  System.Security.Cryptography.CryptographicException: The parameter is incorrect. at System.Security.SecureString.ProtectMemory() at System.Security.SecureString.InitializeSecureString(Char* value, Int32 length) at System.Security.SecureString..ctor(Char* value, Int32 length) at System.Net.UnsafeNclNativeMethods.SecureStringHelper.CreateSecureString(String plainString) at System.Net.NetworkCredential..ctor(String userName, String password) at NopSolutions.NopCommerce.BusinessLogic.Messages.MessageManager.SendEmail(String subject, String body, MailAddress from, MailAddress to, List`1 bcc, List`1 cc) in D:\Tudor\bitstar\GAF\NopCommercePostFinance\Libraries\Nop.BusinessLogic\Messages\MessageManager.cs:line 1459 at NopSolutions.NopCommerce.BusinessLogic.Messages.SendQueuedMessagesTask.Execute(XmlNode node) in D:\Tudor\bitstar\GAF\NopCommercePostFinance\Libraries\Nop.BusinessLogic\Messages\SendQueuedMessagesTask.cs:line 62  
IP address:  
Customer:  
Page URL:  
Referrer:  
Created on:  

Anyone knows what happened?

Edit: Forgot to mention....this is a NopCommerce 1.7