OK, I found my problem, but this is wierd!
I run AFPD on my laptop and I noticed that when on the laptop battery power all was ok. I found two a/c outlets in my house (on the same circuit) cause the USB interface to go crazy. I can replicate this problem at will. I took the laptop to the hobby shop to demo APFD and had the same problem running on a/c power - switch to battery and all is OK! Seems the laptop/interface is sensitive to 'dirty' power. Oh well...threw me for a long time!!