PfSense blocking access to connected subnet with no rule to do so

[SIOE]

Hi,

Setup :

ADSL1 : 192.168.10.1
ADSL2 : 192.168.20.1
LAN : 192.168.1.0/24

pfSense handles WAN failover / basic round robin load balancing on the two ADSL lines.

Up until recently, working fine, no problem. Since the last (2?) update(s) for some reason I can no longer reach 192.168.10.1 on port 80 to manage the router. Traffic passes out from the LAN fine over both interfaces but any attempt to reach 192.168.10.1:80 the packets just get dropped at the pfsense box LAN interface.

A terminal session on the pfSense box reaches port 80 fine. A VM fired up on the same network segment reaches it fine. Reaching 192.168.20.1:80 works fine.

Nothing is logged in the firewall rule log as to why it may be getting dropped, equally nothing is listed as to saying that is passed.

Could someone point me in the correct direction as to why it may be behaving this way?