I have setup IPsec remote VPN, some time, just some time, when clients didn't use 'Enable Transparent Tunneling', the clients could logon, passed user validation, got IPs, but could not access anything internal, failed to ping to any internal IPs. Checked firewall(ASA 5520) logs, it showed the client VPN IP sent packets to internal IPs correctly. But it just failed to access internal networks.
Any clues?