dapper network authentication/search problem

many times after upgrading to the new dapper from breezy, i find that on startup i am unable to access the internet and check my email etc. I have either to restart and switch to the earlier kernel of breezy to get connected
or alternatively
restart the computer and reboot/reset my cable modem too to make dapper find the network.

1--how can i kill/reset the earlier network searching and initialising processes WITHOUT REBOOTING the computer so that it detects the network as was happenning in breezy.

There are certainly some configuration changes made in the startup process which are affecting dapper from linking to the internet whereas this is not the case with the earlier kernel.

2--or let me know which startup configuration file has to be modified and made similar to the earlier one?

Thanks
Kush