Weird MAC in DHCP

Hi, my desktop PC became inaccessible on my LAN after I installed Checkpoint VPN client on it. Client works fine but the PC cannot be pinged from the network, not even locally (pinging itself - 10.0.0.20 from the desktop PC gets no reply even, although I can ping other LAN machines just fine). After I uninstall the VPN client all is fine again.

I've been troubleshooting this for 2 days now - learning routing tables, netbios, ARP, etc. - and among other things I've found a "rogue" MAC address in my D-Link router's DHCP table, registering with various IPs, among them the actual IP of my desktop PC. After router reboot it sooner or later registers with other IPs though.

The rogue MAC has an "infinite" lease on the DHCP (although it's set for limited leasing) and the address is 00-4F-62-27-4A-FA which resembles the LAN MAC of my Ovislink access point which has this configuration:

DHCP disabled
IP Protocol Fixed IP
br0 IP Address 10.0.0.3
br0 Subnet Mask 255.255.255.0
br0 Default Gateway 10.0.0.1 (the D-Link)
br0 MAC Address 00:4f:62:27:4a:f9


Now how on earth could the Ovislink do this (if it is the actual culprit that is) and could this be the reason for my LAN issue? I've tried to clear and check again the ARP cache on the other PCs and I have removed the offedning entry from local ARPs but this MAC is still registering with the DHCP and I still cannot reach the desktop.

Thank you for any suggestions!