ethernet after boot problem

[Yigal Weinstein]

averatec 3200 series with 2.6.12 kernal.  dchp3-client works on boot to give me internet etc iff ethernet cable is plugged into the laptop.   If i plug in the ethernet cable after boot there seems to be no way to get internet.  i don't know my way around network configuration and the suggestions given in deb. manual etc. and through user groups dont seem to help.  i haven't included any information about the connection because 1. i probably dont know what i am looking for and 2. i dont know what is needed to solve this problem.   tell me what would help you and  i will send what ever it is. 

The laptop has dhcp3-common, dhcpd, dhcp3-client, laptop-net (which I am not using presently) installed.

Any help would just be great,

Yigal Weinstein