Duplicate IP Error

Hi, We have recently had our network rebuilt by a contractor from a messy, unmanaged, plate of spaghetti to a managed, neat, workhorse. Unfortunately since then, nothing works properly anymore. Anyway, in trying to track to the causes of some of the issues we are having we have come across something odd that we think may point to a solution. All of our 10.4.x machines (including servers) are now continuously complaining of a duplicate IP address in use. The odd thing is that the MAC address they report as using this address is their own. Does anybody know of a bug or incompatibility that may be causing this? We are using HP Procurve switches (4160gl, 2824, 2848, 2626) For example my machine: - G5, 2GhzDP 1.5GB, 10.4.7. IP 10.1.1.198, MAC 00:14:51:11:58:86 system.log from this morning: - [code] Nov 29 10:40:07 CP-IT-01 kernel[0]: en0 duplicate IP address 10.1.1.198 sent from address 00:14:51:11:58:86 Nov 29 10:40:07 CP-IT-01 kernel[0]: en0 duplicate IP address 10.1.1.198 sent from address 00:14:51:11:58:86 Nov 29 10:40:07 CP-IT-01 kernel[0]: en0 duplicate IP address 10.1.1.198 sent from address 00:14:51:11:58:86 Nov 29 10:40:07 CP-IT-01 kernel[0]: en0 duplicate IP address 10.1.1.198 sent from address 00:14:51:11:58:86 Nov 29 10:40:07 CP-IT-01 kernel[0]: en0 duplicate IP address 10.1.1.198 sent from address 00:14:51:11:58:86 Nov 29 10:40:07 CP-IT-01 kernel[0]: en0 duplicate IP address 10.1.1.198 sent from address 00:14:51:11:58:86 Nov 29 10:40:07 CP-IT-01 kernel[0]: en0 duplicate IP address 10.1.1.198 sent from address 00:14:51:11:58:86 Nov 29 10:40:07 CP-IT-01 kernel[0]: en0 duplicate IP address 10.1.1.198 sent from address 00:14:51:11:58:86 Nov 29 10:40:07 CP-IT-01 kernel[0]: en0 duplicate IP address 10.1.1.198 sent from address 00:14:51:11:58:86 Nov 29 10:40:07 CP-IT-01 kernel[0]: en0 duplicate IP address 10.1.1.198 sent from address 00:14:51:11:58:86 Nov 29 10:40:07 CP-IT-01 kernel[0]: en0 duplicate IP address 10.1.1.198 sent from address 00:14:51:11:58:86 Nov 29 10:40:07 CP-IT-01 kernel[0]: en0 duplicate IP address 10.1.1.198 sent from address 00:14:51:11:58:86 Nov 29 10:40:07 CP-IT-01 kernel[0]: en0 duplicate IP address 10.1.1.198 sent from address 00:14:51:11:58:86 Nov 29 10:40:07 CP-IT-01 kernel[0]: en0 duplicate IP address 10.1.1.198 sent from address 00:14:51:11:58:86 Nov 29 10:40:07 CP-IT-01 kernel[0]: en0 duplicate IP address 10.1.1.198 sent from address 00:14:51:11:58:86 Nov 29 10:40:07 CP-IT-01 kernel[0]: en0 duplicate IP address 10.1.1.198 sent from address 00:14:51:11:58:86 Nov 29 10:40:07 CP-IT-01 kernel[0]: en0 duplicate IP address 10.1.1.198 sent from address 00:14:51:11:58:86 Nov 29 10:40:07 CP-IT-01 kernel[0]: en0 duplicate IP address 10.1.1.198 sent from address 00:14:51:11:58:86 Nov 29 10:40:07 CP-IT-01 kernel[0]: en0 duplicate IP address 10.1.1.198 sent from address 00:14:51:11:58:86 Nov 29 10:40:08 CP-IT-01 kernel[0]: en0 duplicate IP address 10.1.1.198 sent from address 00:14:51:11:58:86 Nov 29 10:40:08 CP-IT-01 kernel[0]: en0 duplicate IP address 10.1.1.198 sent from address 00:14:51:11:58:86 Nov 29 10:40:08 CP-IT-01 kernel[0]: en0 duplicate IP address 10.1.1.198 sent from address 00:14:51:11:58:86 Nov 29 10:40:08 CP-IT-01 kernel[0]: en0 duplicate IP address 10.1.1.198 sent from address 00:14:51:11:58:86 Nov 29 10:40:08 CP-IT-01 kernel[0]: en0 duplicate IP address 10.1.1.198 sent from address 00:14:51:11:58:86 Nov 29 10:40:08 CP-IT-01 kernel[0]: en0 duplicate IP address 10.1.1.198 sent from address 00:14:51:11:58:86 Nov 29 10:40:08 CP-IT-01 kernel[0]: en0 duplicate IP address 10.1.1.198 sent from address 00:14:51:11:58:86 Nov 29 10:40:08 CP-IT-01 kernel[0]: en0 duplicate IP address 10.1.1.198 sent from address 00:14:51:11:58:86 Nov 29 10:40:08 CP-IT-01 kernel[0]: en0 duplicate IP address 10.1.1.198 sent from address 00:14:51:11:58:86 Nov 29 10:40:08 CP-IT-01 kernel[0]: en0 duplicate IP address 10.1.1.198 sent from address 00:14:51:11:58:86 Nov 29 10:40:08 CP-IT-01 kernel[0]: en0 duplicate IP address 10.1.1.198 sent from address 00:14:51:11:58:86 Nov 29 10:40:08 CP-IT-01 kernel[0]: en0 duplicate IP address 10.1.1.198 sent from address 00:14:51:11:58:86 Nov 29 10:40:08 CP-IT-01 kernel[0]: en0 duplicate IP address 10.1.1.198 sent from address 00:14:51:11:58:86 Nov 29 10:40:08 CP-IT-01 kernel[0]: en0 duplicate IP address 10.1.1.198 sent from address 00:14:51:11:58:86 Nov 29 10:40:13 CP-IT-01 kernel[0]: en0 duplicate IP address 10.1.1.198 sent from address 00:14:51:11:58:86 Nov 29 10:40:13 CP-IT-01 kernel[0]: en0 duplicate IP address 10.1.1.198 sent from address 00:14:51:11:58:86 Nov 29 10:40:13 CP-IT-01 kernel[0]: en0 duplicate IP address 10.1.1.198 sent from address 00:14:51:11:58:86 Nov 29 10:40:16 CP-IT-01 kernel[0]: en0 duplicate IP address 10.1.1.198 sent from address 00:14:51:11:58:86 Nov 29 10:40:16 CP-IT-01 kernel[0]: en0 duplicate IP address 10.1.1.198 sent from address 00:14:51:11:58:86 Nov 29 10:40:16 CP-IT-01 kernel[0]: en0 duplicate IP address 10.1.1.198 sent from address 00:14:51:11:58:86 Nov 29 10:51:56 CP-IT-01 kernel[0]: en0 duplicate IP address 10.1.1.198 sent from address 00:14:51:11:58:86 Nov 29 10:51:56 CP-IT-01 kernel[0]: en0 duplicate IP address 10.1.1.198 sent from address 00:14:51:11:58:86 Nov 29 10:51:56 CP-IT-01 kernel[0]: en0 duplicate IP address 10.1.1.198 sent from address 00:14:51:11:58:86 Nov 29 11:00:16 CP-IT-01 kernel[0]: en0 duplicate IP address 10.1.1.198 sent from address 00:14:51:11:58:86 Nov 29 11:00:16 CP-IT-01 kernel[0]: en0 duplicate IP address 10.1.1.198 sent from address 00:14:51:11:58:86 Nov 29 11:00:16 CP-IT-01 kernel[0]: en0 duplicate IP address 10.1.1.198 sent from address 00:14:51:11:58:86 Nov 29 11:00:44 CP-IT-01 kernel[0]: en0 duplicate IP address 10.1.1.198 sent from address 00:14:51:11:58:86 Nov 29 11:00:44 CP-IT-01 kernel[0]: en0 duplicate IP address 10.1.1.198 sent from address 00:14:51:11:58:86 Nov 29 11:00:44 CP-IT-01 kernel[0]: en0 duplicate IP address 10.1.1.198 sent from address 00:14:51:11:58:86 Nov 29 11:01:33 CP-IT-01 kernel[0]: en0 duplicate IP address 10.1.1.198 sent from address 00:14:51:11:58:86 Nov 29 11:01:33 CP-IT-01 kernel[0]: en0 duplicate IP address 10.1.1.198 sent from address 00:14:51:11:58:86 Nov 29 11:01:33 CP-IT-01 kernel[0]: en0 duplicate IP address 10.1.1.198 sent from address 00:14:51:11:58:86 [/code]