The error that you are getting on this update page is referencing line 173 which is where you have the iRite instance. The cStr function is being used around the value from your db like this:
This tells me that the value inside of this cStr is equating to Null. You should try assigning this value to a variable, then do a check for null, if it is then set the value to be "". You can use the IsNull function for asp, it looks like this:
returns true or false based on the value of the parameter
Dim theVal = rsPropertyTable.Fields.Item("Content").Value
If IsNull(theVal) Then
theVal = ""
Then just use this variable for the value of your editor on the page.