System.Diagnostics.Process.Start not opening the PDF document

I am using Dot Net 1.1 win form based application on Windows XP SP2.
Code is written on VB.Net but does not matter can be done with any dotnet language.

System.Diagnostics.Process.Start not opening the PDF document on one client machine.
Adobe Acrobat PDF reader 8.0 is installed on all client machines.

Same code is able to open other files like jpg, bmp, doc, xls...
I doubt if .pdf is not associated with the acrobat on the windows but it is also fine.
If I open the PDF file directly by double clicking it, it is opening, working fine.
A year ago or bit less earlier Acrobat 7 and earlier Acrobat 5 was also installed but then later all uninstalled and now is only Adobe Acrobat 8.0
The path of the file itself is perfectly fine, the problem is not with the spaces in the path of file name.
Same thing is working on all client machine but not on one machine.Start Free Trial

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Public Sub OpenDocument(ByVal FilePath As String, Optional ByVal bUseShellExec As Boolean = True, Optional ByVal bPrint As Boolean = False)
		'MsgBox(FilePath)
 
		Dim Print As New System.Diagnostics.ProcessStartInfo
		'Verb is being always used as "open"
		If bPrint = False Then
			Print.Verb = "open"
		Else
			Print.Verb = "Print"
		End If
		Print.WindowStyle = ProcessWindowStyle.Maximized
		Print.FileName = FilePath
		Print.UseShellExecute = bUseShellExec
		Try
			System.Diagnostics.Process.Start(Print)
		Catch ex As System.ComponentModel.Win32Exception
			MsgBox(ex.Message & vbCrLf & ex.StackTrace)
		End Try
	End Sub