What do you have between the ADSL and your LAN before you connected directly to the ADSL router (or whatever) ???
Here i'm using a common switch with 8 ports between the ADSL router and the LAN.
The SME 5.5 is configured as "server only" but delievers the services; FTP, Mail, HTTP and File&Print without any delays.
Maybe you should try to connect some other hub/switch in your system before making some other "drastic" movements.
Rgs tmn