Add an ACL that blocks the traffic. Something along those lines (will need to be more tailored):
ip access-list extended AL-INSIDE-1
deny ip 192.168.1.0 255.255.255.0 192.168.10.0 255.255.255.0
permit ip 192.168.1.0 255.255.255.0 any
ip access-list extended AL-INSIDE-10
deny ip 192.168.10.0 255.255.255.0 192.168.1.0 255.255.255.0
permit ip 192.168.10.0 255.255.255.0 any
int fa0/0
ip access-group AL-INSIDE-1 in
int fa0/1
ip access-group AL-INSIDE-10 in
May need to tweak this - I don't know all the details of your setup but that should get you going pretty well.