We have collected more information. This happens exactly at the same time one specific server reboots. The other two servers that are affected are using the same SQL Server which resides on another server. So, this data connection error was similar to both ASP.NET applications because they are using the same SQL Server host. So, this seems to target that there is a conflict at reboot time for the other server when the SQL Server related services are being loaded.

Anyone would know what type of conflict could be in effect here?