I had similar problems, using a DLink Wireless network link to the DLink router connected to the STB. Eventually, some genius sent me the following
"Disable APIPA on a specific NIC HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Servic es\Tcpip\Parameters\Interfaces\<adapter name>
On the Edit menu, Add Value name IPAutoconfigurationEnabled, as a REG_DWORD data type, and set the data value to 0. The default (missing) value is 1, which enables APIPA on this interface.
Disable APIPA on the Entire Computer
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Servic es\Tcpip\Parameters
On the Edit menu, Add Value name IPAutoconfigurationEnabled, as a REG_DWORD data type, and set the data value to 0. The default (missing) value is 1, which enables APIPA on ALL interfaces.
You must restart the PC for the change to take effect."
Basically, my understanding is that the PC looked for the network, couldn't find it in time and started looking at its own arse, hence the 169.x.x.x address. This adjustment to the registry seemed to stop it hunting its arse but had to be re-done after some windows upgrades. Now, all seems ok except that I had to use a manual IP address inside TCP/IP properties. Possibly it took so long because the D Link card was failing, but a few quid sorted that out.
Hope this helps