grlnxtdr88,
No, I would not attempt to access and flush the device.
Most nurses first concern is that of a blood clot at the distal end. But, even if there wasn't a clot present, the catheter is covered in biofilm and flushing after all this time without appropriate maintenence of the catheter can cause bacteria to rush into the venous system. It is a shame that the surgeons feel that they should leave it in.
Since the patient was able to tell you that the previous RN had difficulty accessing the port, hopefully the pt will be able to convey to anyone who wants to access it, that it is not a viable line. If the pt is in an emergency situation, perhaps a sticker placed over the site saying, "non-patent port" would suffice.
Anyway, that's my 2 cents worth.

DD