I've not been using Linux for more than 1 week. But yesterday when I boot Linux, it was so slow and that slowness started from

Starting logger
.....

and so slow in : Starting sendmail

and after booting, all applications like Mozilla or Terminal started up very slowly

It didn't happen before, so what made the slowness ?

Any idea appreciated.

Try opening a terminal and running "top". This will show the processes that are running. You can press "P" and "M" to sort my proccessor or memory usage. This way you should be able to see what is using all of your system resources.

Is this happening all the time or just on one boot?

According to "top", CPU usage always below 50% (sometimes 0.99%) so I thought that's not the problem.
I tried to reboot several times but it's still happening. It took more than 5mins to boot up (only more than 2 mins before)

What about the memory usage?

Have you installed anything or changed any configuration recently?

Are you running X or is this a console only system? If you are running X try the system without a GUI and see if the problem persists.

This sounds like a name lookup problem. If you have changed your hostname or changed the settings in /etc/nsswitch.conf this could sometimes be a problem.
Usually you get some kind of error message while login in to Gnome or KDE if this is the problem.

Anything special you remember that you have done lately concerning hostname or name lookup settings?

Mozilla use the most memory : 4%
I'm running in KDE, I've got to remember what've i done recently.

I'm sure I never messed around with hostname or name lookup setting, I don't even know what it is.
The last thing I did in Linux is practising with some Shell command and listen some music.

Here's my /etc/hosts
# Do not remove the following line, or various programs
# that require network functionality will fail.
127.0.0.1 localhost.localdomain localhost


and my /etc/nsswitch.conf

#
# /etc/nsswitch.conf
#
# An example Name Service Switch config file. This file should be
# sorted with the most-used services at the beginning.
#
# The entry '[NOTFOUND=return]' means that the search for an
# entry should stop if the search in the previous entry turned
# up nothing. Note that if the search failed due to some other reason
# (like no NIS server responding) then the search continues with the
# next entry.
#
# Legal entries are:
#
# nisplus or nis+ Use NIS+ (NIS version 3)
# nis or yp Use NIS (NIS version 2), also called YP
# dns Use DNS (Domain Name Service)
# files Use the local files
# db Use the local database (.db) files
# compat Use NIS on compat mode
# hesiod Use Hesiod for user lookups
# [NOTFOUND=return] Stop searching if not found so far
#

# To use db, put the "db" in front of "files" for entries you want to be
# looked up first in the databases
#
# Example:
#passwd: db files nisplus nis
#shadow: db files nisplus nis
#group: db files nisplus nis

passwd: files
shadow: files
group: files

#hosts: db files nisplus nis dns
hosts: files dns

# Example - obey only what nisplus tells us...
#services: nisplus [NOTFOUND=return] files
#networks: nisplus [NOTFOUND=return] files
#protocols: nisplus [NOTFOUND=return] files
#rpc: nisplus [NOTFOUND=return] files
#ethers: nisplus [NOTFOUND=return] files
#netmasks: nisplus [NOTFOUND=return] files

bootparams: nisplus [NOTFOUND=return] files

ethers: files
netmasks: files
networks: files
protocols: files
rpc: files
services: files

netgroup: files

publickey: nisplus

automount: files
aliases: files nisplus

check ou the bootlog file for the sendmail and others that are slow to start .
it cuold give a clue.

Guys!
Now I know the problem is the network. When i plugged the network cable out, it booted up as fast as before. But when plug in, it's slow again.
(but network in Window still fast)

So how to fix that ? (I'm using DHCP)