Hi Mini M,
I have not personally done what you are trying to do, but I found a link that might help you out. This
one is for a USB to Serial adapter, so it is a little different than what you are using, but it talks about needing a driver, which might be the same for your case.
Have you used Measurement and Automation Explorer (MAX) to try to communicate with your serial port? I would suggest trying to open a VISA session in MAX and write and read to your port. Once you can do this successfully you should be able to communicate in LabVIEW. If you are not familiar with how to use MAX, repost and I will walk you through it.
Another thing to try is the serial examples that ship with LabVIEW. You can find them by opening LabVIEW>>Help>>Find Examples, this will launch the NI Example Finder. Go to the search tab and type "serial", this will bring up some serial examples that you can experiment with.
Hope this helps!
JenK