Acrobat Standard 9 : app.viewerVersion is throwing error.

[ManojR@adobeforums.com]

I'm using Acrobat 9 standard in Windows platform.
I have a vb 6.0 application and I have to find the version of
Acrobat installed on the user machine. I'm using the below code but it is throwing error :

Error Message:
"
Run-time error '-2147417851 (80010105)':
Automation error
The server threw an exception "

How can I find the version of Acrobat available in a
machine? The below code works with Acrobat 8.0
installed machine but fails with Acrobat 9.0 standard

Dim oAVDoc As Acrobat.CAcroAVDoc
Dim oPDDoc As Acrobat.CAcroPDDoc
Dim oJSO As Object
Dim iOK As Boolean
Private Sub Form_Load()
Set oAVDoc = CreateObject("AcroExch.AVDoc")
iOK = oAVDoc.Open ("<< required parameters>>")
Set oPDDoc = oAVDoc.GetPDDoc
Set oJSO = oPDDoc.GetJSObject
MsgBox (oJSO.App.viewerVersion)