This can happen when you have a duplicate IP on the network.
To check if it is the case:
If you cannot open the webpage, but still ping the IP.
Please run the 'arc -a' command from a command prompt on the PC you are trying to open the login page from.
It will list all the IP's and physical addresses.
Make note of the physical address for the AMETHYST IP.
When you are able to log into AMETHYST again, run the arc command again. Now match the physical address against the previous one.
If it is two different physical addresses, then you have a duplicate IP on the network.
Please ask you IT/Network support to sort it out.