Since this printer worked when connected to the old DP-300U I knew Vista drivers weren't the issue. I configured the port manually (via Add network printer) as a standard TCP/IP port (see below) and am back in business.
The first time I tried that, however, I got "A port by that name already exists" (for "dlink-xxxxxx_9100"), even though the printer that setup tried to add didn't show up anywhere. I found the name in the registry, however, and after exporting the settings deleted the following key, where "xxxxxx" was the last six characters of the DPR-1260's MAC address (your port number, 9100 below, may also be different):
[HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Print\Monitors\Standard TCP/IP Port\Ports\dlink-xxxxxx_9100]
I also found I had to reboot after doing that, but was then able to add the printer. But first, several digressions...
The Quick Guide says to access the DPR-1260's interface via "http://dlink-xxxxxx". This worked fine from the first machine (a desktop with a wired connection to the same router that the DPR-1260 was connected to). However on all the wireless laptops, I had to use the actual IP address (obtained from the router's DHCP client table). If it matters, the router and WAP are LinkSys components, not D-Link.
Also, make sure your firewall is set up to trust devices on the local network (you may have to add individual names or IP addresses).
To add the printer, do Control Panel->Printers->Add Printer, then:
- Click the "Add Network printer..." link.
- It will start searching. Click Stop, then Click the "The printer I want isn't listed..." link.
- Select the "Add printer using a TCP/IP address" radio button and click Next
- Select "TCP/IP devices" and enter your device name, e.g., "dlink-xxxxxx"; append "_9100" to the value in the port name box. Be sure "contact the printer" is checked. Click Next
- it will contact the printer, then ask for more information. (BTW, this is where you'd get the "port name already exists" message if you'd previously tried to use Setup.)
- On "Additional Information", select Custom and click the Settings button.
- You should see Raw selected, and port 9100 filled in. Check "enable SNMP" and click Next (or maybe it was OK)
- In the install drivers dialog, select HP on the left, and "hp officejet series 6100" on the right. Click Next (or OK) again.
- Optionally, chek the box to make it your default printer. Print a test page.
The above procedure was the norm for the DP-300U. While the Setup Wizard is great (when it works), the steps to configure the printer via Windows should also be covered in the full manual (they are not even mentioned).
The Quick Guide should also make it clear that you don't have to disconnect the wired connection after configuring your attached printers: a wired connection is faster, and using it eliminates any issues that could arise if you make changes your network's wireless security config.
Finally, mention someplace on the packaging that only true USB printers are supported, not older printers (like my HP Laserjet 6L) using a "parallel to USB" cable (these require installation of drivers on the host, and there's no way to do that on the DPR-1260).
Update...With the 6100 series drivers, I was not getting the duplexing options supported by the printer. OTOH, the Services tab appeared, and the Calibrate service worked ok. There was no "ink level" service, though, which would have been useful. This does suggests that the DPR-1260 is passing advanced codes, which I do not think was the case with the DP-300U.
In any case I switched to the 990C drivers and got my duplexing capability back (but no Services tab).