What do you mean "dropping all packets to two remote networks"? Do you mean packets from the outside interface, going to these two networks on the inside aren't getting through?
Are you sure there isn't an ACL or something similar on another device in between these two networks and the PIX? Can you ping anything on these networks from the PIX itself? Does the PIX have valid route statements pointing to a valid next hop in it's configuration? Do the two remote networks have routes back to wherever you're trying to connect from?
If nothing appears in the syslog then there's a good chance the packets aren't even reaching the PIX, or they're passing through the PIX as you would expect.