|Used to have a DI604 and I agree with wanderer 100%. They're a pretty stable unit and barring a hardware malfunction, they should work just fine.|
If you still have problems after resetting to factory defaults (done by holding the reset button in for about 8 seconds and then letting the unit reboot) then you may need to replace the unit.
NOTE: I don't remember the default IP offhand, I believe it's either 192.168.1.1 or 192.168.0.1. You can likely find the manual or setup guide online to confirm.