Can't delete old routers or create certain other ones?

Hi all. I have two related problems.

1) I have two entries under “Routers” that, when I click on them, I get the message, “Unable to find object”. I need to delete them and recreate them, since the devices with those IP addresses have changed. I tried the repairdb.bat/sh procedure, and it went through with no errors, but the problem remains.

2) I cannot create a device with one particular IP address of 192.168.y.z. When I try, I get the message, “Entries for the device are either partially added or removed. Click [here...] to remove and readd the device.” How do I make it so I can add that device?

Thanks in advance,

Brian