Hi there,
I found today what I think is a bit of a bug - if I add the Custom Field "Location" to the IP addresses then it breaks the View on the Manage Subnets and IP addresses.
The Subnets themselves are still viewable - but the IP addresses disappear and it just says there are no IPs. I found if I delete the Location field they all come back. I then renamed the field to DeviceLocation and everything works - just seems to be something weird with using the name Location that it didn't like. I tried this several times and it broke everytime when I used Location as a field name.
I wondered if this was maybe a conflict with the Location field on the Subnets which isn't a custom field?