FormattedIO.ReadBinaryBlockOfByte

I am trying to read binary trace data from RS spectrum analyser.  I have had this working before with VisaNS.dll 13.0.45.167, but NI seem to have introduced changes that mean that my code no longer works.

I can use NI MAX to execute the commands manually and get the correct data from the spectrum analyser I am trying to use.

"FORM REAL,32"

"TRACATA? TRACE1"

Read two bytes: #4

Read four bytes: 2004

Read 2005 bytes: ... correct data...

Using VB2013 the following command  returns exception "The binary block header was not found in the input stream":

Dim byteData(2004) As Byte

Session.FormattedIO.ReadBufferSize = lngBytes + 1               - omitting this command makes no difference.

byteData = Session.FormattedIO.ReadBinaryBlockOfByte()

I know that the Session is good as it returns the #4 and 2004 that I get with NI MAX.

I have the following references:

- NationalInstruments.Visa.dll - 13.0.45.167

- Ivi.Visa.dll - 5.8.908.0

Any ideas would be gratefully received.