StreamReader/Writer Error On Close?

I was able to code a sub that opens a StreamReader and Writer. The Reader reads a *.txt file and the Writer modifies it line by line as it's entered into the memory then writes it to a temporary file which is then copied over the file that the Reader read.

The problem is that the StreamReader and Writer seem to fail to close.At first when I tested it I would get an error stating:

Object reference not set to an instance of an object

I put breakpoints in the sub to figure out where it's erroring out and it's erroring out when it does sr.close() and sw.close() (Reader/Writer.close())Here's the code for the sub. Maybe someone can tell me what I did wrong.

Private Sub Button2_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button2.Click
If pDebugMessages = True Then MsgBox("Stream Reader/Writer initialized.", MsgBoxStyle.OkOnly, "Debug")
Try

[code].....