I wonder if something else is locking the port.
Try this before starting the Arduino IDE:
ls -l /dev/ttyUSB0
Please paste the output here
And try:
cat /dev/ttyUSB0
if it shows nothing or if it shows some serial data being sent from the Arduino then it should be ok.
If something else is locing the port it would show cat: /dev/ttyUSB0: Device or resource busy
What kind of sketch is on your chip? Something that send serial data?
crw-rw---- 1 root dialout 188, 0 2012-05-08 16:09 /dev/ttyUSB0
i´ts sould be ok, i give the user right for dialout
cat: /dev/ttyUSB0: Device or resource busy
yes it send serial data as a sting but only if i send a sting to the arduino
i googled abit about:
cat: /dev/ttyUSB0: Device or resource busy
i found this to find what process is accessing the arduino
sudo lsof | grep ttyUSB
but i get this error
lsof: WARNING: can't stat() fuse.gvfs-fuse-daemon file system /home/home/.gvfs
Output information may be incomplete.
upowerd 1393 root 14u CHR 188,0 0t0 8451 /dev/ttyUSB0
linux is so complicatet if you never use it 
The error you get is just a warning. Doesn't mean anything in this case.
What I can see is that upowerd is locking the device.
Upower is a power save component and there seems to be an old bug related to Upower and the FTDI chip: http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=586751
You will have to upgrade or disable Upower to solve this but I'm not sure how to do it. As the problem is not with your board or with the Arduino environment there may be better support forums than this one.
You may have to Google a bit.
perhof:
You will have to upgrade or disable Upower to solve this but I'm not sure how to do it
sudo apt-get remove upower
Removing it may disable support for battery monitoring (if it's a laptop) and features like suspend/hibernate. You may or may not not care about this.
thanks alot guys and special thanks to perhof 
it work now i update my xubuntu to 12.04. your answer about the upower bug. i google abou it and its fixed in the 12.04 thanks
okey now i have another problem -.-
avrdude stk500_recv() programmer is not responding
this is what i get if i try to upload code
A few questions:
What kind of Arduino board do you have?
Which Arduino version do you have installed on the server.
Was it when you upgraded to 12.04 that it stopped working?
acidcoolxxx:
avrdude stk500_recv() programmer is not responding
This means that the IDE thinks you're using a specific programmer device, rather than a bootloader-based serial uploader.
You must have edited your boards file, or selected "update using programmer" in the IDE. Re-select the right board using the serial port, and you should be good to go.
if i try update using programmer i get this error
avrdude: usbdev_open(): did not find any USB device "usb"
hmmm.... this is pretty annoying
You probably configured the wrong programmer type, then. What type of programmer are you using? The name of the USBtinyII is "usbtiny" not "usb" for example.