Firewall – IP Address Conflict with Router/Firewall

I've been having IP issues with my local box for a couple months now. Usually when it starts acting up I don't have the patience to look into it, so I just drop onto DHCP, but this morning I've finally decided to figure out what's going on.

I'm on a network that has 192.2.40.1 as the gateway, and is a 255.255.254.0 subnet (so IP Range is 192.2.40.1-192.2.41.254). My static IP address is 192.2.40.17. We have a Watchguard Fireware XTM Firewall/Router that sits on 192.2.40.1 . Also, our DHCP range is 192.2.41.200-192.2.41.254

The issue is that I occasionally lose my network connection, and when I try to reconnect I get errors regarding an IP Address conflict. We're pretty strict about documenting IP addresses here, so I found it quite odd that someone else would be using my IP address. I did a couple network scans, checked my DNS and DHCP logs, and found nothing using 192.2.40.17 (aside from my computer).

Grasping at straws, I ran "arp -a" to check if that could give me any information. Oddly enough, this is what I saw (note: I am on DHCP right now):

C:\Users\jwegner>arp -a

Interface: 192.2.41.107 --- 0xa
  Internet Address      Physical Address      Type
  192.2.40.1            00-90-7f-42-3f-30     dynamic
  192.2.40.17           00-90-7f-42-3f-30     dynamic
  //Truncated, because the rest is not important

Interesting – it would appear that my local computer is viewing 192.2.40.1 and 192.2.40.17 as the same device. I checked that MAC Address, and it is indeed the MAC Address for our firewall/router. I cleared my arp cache, thinking that something just got turned around somewhere. I then pinged 192.2.40.17 to recache the arp, and arp -a output the same thing.

There is nothing in my Firewall/Router that would make it take over the 192.2.40.17 address. Also, if I ping 192.2.40.17 I get nothing, so I must be getting some sort of false positive here. Any ideas on what might be causing this?