Is this a flat network or do you have multiple vlans setup? If you are seeing this with all different devices, then you can eliminate that out the picture... most of the time. So basically they are unable to get to a certain server but still has network connectivity? Tough to say... I would either try to update on client device driver and see if that helps, if not, try a different code to see if that is your issue. I'm running a 871W at home, but still on the 12.3 code.