>On the assumption that this is ADO.NET: what is the value of the Command.CommandTimeOut property (the default is 30 secs so you may want to increase it ....)

You are right. SQLExec() and SQLDelete() classes of my data class have it set to 0 to rely on the IIS timeout instead. But, I will do the same for SQLUpdate() and SQLInsert().

However, this situation has been caused in the middle of the night. The traffic was pretty much empty. So, could it be that SQL Server falls in sleep mode or releases its cache when not being accessed for a while? If that would the case, it is known that the first data hit on some big tables will always take longer. Then, they respond in a flash. So, I am wondering if that was the cause of the situation.