1. First you have to change the IP settings of your computer to manual.
Your router leases 192.168.0.x to ypur pc by dhcp (automatically).
But the cube has 192.168.1.254

So you need to change the IP address of your pc to 192.168.1.x (x = something between 1 and 253).

2. After changing the ip of your PC, you should be able to connect to the webinterface of the cube. Once you got connected, change the IP of the cube to 192.168.0.x (x = something between 2 and 254)

3. Then change the IP of your PC from manual back to automatically (DHCP). You should now be able to connect to the cube by his new IP Address you set in step 2.

Good luck