When you connected directly to the computer - did you set a static ip address on the computer?
When you connected through the router - did you do so with the NAS on or off?
When you connected the NAS to the router - what lights were amber and what does the light tell you?
In most cases when EasySearch detects the NAS but it cannot be configured, the problem lies with ip addressing - EasySearch uses ethernet broadcast technology to locate the NAS, but cannot connect to the NAS' web server because that requires tcp/ip.
If you connect the NAS to the router after switching it on, you could also create a situation where the NAS having defaulted to a static ip address does not request an address from the router and so, cannot be reached - however - there may be another problem, since EasySearch should still find it - but since there are no green/yellow LEDs on the NAS, those lights must have been on your router - so get the router manual and find out what they are telling you.
A flashing hard drive LED at startup, in my experience a problem of some sort with the particular drive - it may have a problem, it may not have been detected by the NAS for one reason or another, many high capacity drives have a delayed or stagger spin option - check the drive documentation to see if it does and try disabling it.
Whilst the NAS, as pointed out in the previous response "likes an unpartitioned" drive, installing a drive with a partition on it, in my experience, will not cause it to fail - you should be aware however, that you cannot use the drive without repartitioning it and losing whatever data is stored on it.