ok,
i can ping the external and internal interface
i can ping the internal devices by ip and dns
i can ping domains on the web and do a name resolution. tracert gives also valid answers.
if i put a domain in the web browser, it says "website found" but has a timeout after certain time. (only for external domains)
if i update the network settings through web admin, imm. it starts working
It would be useful if you described your internal & external network topology and what each devices is and how it relates to the devices its attached to.
Some questions;
Can you boot an MD successfully on your LAN side NIC? If you attach another computer to your LAN side NIC does it get a valid DHCP address? Have you got a 2nd DHCP server on your LAN side?
All the best
Andrew