Try creating a variable setting the vairbale equal to your string and passing in the variable to the execute. Have seen builing a string throw issues before.

Dim strSQL

strSQL = "EXEC InsertNextPage @StoryID='" & Request.Form("StoryID") & "', @SubscriberID='" & Request.Form("SubmitterID") & "', @Content='" & Cleanse(Request.Form("SubmittedPage")) & "'"

conn.Execute strSQL

If it fails then try showing the value of strSQL to make sure it looks correct.