ttyacm0 port shows up but does not work

Hello,
today I started the programming sequence and had no arduino pluged in. While the sequence was started i plugged the aruino Leonardo in one of the usb ports. But till then the Arduino can not be programmed until i hit the reset switch.
What is more suprising, is that after I restart the arduino 1.6.3 IDE the port ttyacm0 shows up but vanishes after I start serial monitor or programming und I get the error that ttyACM0 is not avaible.

My OS is Ubuntu 15.04

What could be wrong???

So here is the dmesg:

[ 1437.904022] usb 5-1: new full-speed USB device number 24 using uhci_hcd
[ 1438.088058] usb 5-1: New USB device found, idVendor=2341, idProduct=0036
[ 1438.088062] usb 5-1: New USB device strings: Mfr=2, Product=1, SerialNumber=0
[ 1438.088065] usb 5-1: Product: Arduino Leonardo
[ 1438.088068] usb 5-1: Manufacturer: Arduino LLC
[ 1438.091116] cdc_acm 5-1:1.0: ttyACM0: USB ACM device
[ 1445.740046] usb 5-1: USB disconnect, device number 24
[ 1445.980020] usb 5-1: new full-speed USB device number 25 using uhci_hcd
[ 1446.100040] usb 5-1: device descriptor read/64, error -71
[ 1446.324020] usb 5-1: device descriptor read/64, error -71
[ 1446.540018] usb 5-1: new full-speed USB device number 26 using uhci_hcd
[ 1446.660017] usb 5-1: device descriptor read/64, error -71
[ 1446.884016] usb 5-1: device descriptor read/64, error -71
[ 1447.100018] usb 5-1: new full-speed USB device number 27 using uhci_hcd
[ 1447.508012] usb 5-1: device not accepting address 27, error -71
[ 1447.824040] usb 5-1: new full-speed USB device number 28 using uhci_hcd
[ 1448.240018] usb 5-1: device not accepting address 28, error -71
[ 1448.240044] usb usb5-port1: unable to enumerate USB device

So the arduino does not show up on Mac OS X 10.10 . I think I have to reupload the bootloader???

So somehow forget my previous post. Mac Os X does recognize it properly if not plugged in while in sleep mode.

So my solution for ubuntu 15.04 is:

sudo apt-get remove brltty .

Pretty easy! i found it on a tut from ladyada. I do not know why this was installed on my system.