I type command of ROS,but no reaction!

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This phonemenon seldom occurs,but i have seen it several times in the past months. my operations are followings:

1. Start my ubuntu,then open a terminal
2. I type "roscore",however nothing appears...

after i wait about several minutes .i see the following,and i go on my waiting :

... logging to /home/bobliao/.ros/log/49c47ac0-1117-11e2-976a-74ea3a7e2629/roslaunch-bob-r-2600.log
Checking log directory for disk usage. This may take awhile.
Press Ctrl-C to interrupt
Done checking log file disk usage. Usage is <1GB.

after 10 minutes , it prints the error info ,and that's an error of MASTER_URI configuration problem. but why this error make the terminal so slow?there must be something else,as ordinary it will print the error immediately.

i am only working on the single mode,all the ros nodes are on the same machine. here , i paste related lines of my .bashrc file :

export ROS_PACKAGE_PATH=$ROS_PACKAGE_PATH:~/fuerte/

export ROS_WORKSPACE=~/fuerte

source /opt/ros/fuerte/setup.bash

export ROS_MASTER_URI=http://192.168.1.101:11311

export ROS_HOSTNAME=192.168.1.101

my network configuration:on PC,i use a wireless card,connected to a router.and when i run my PC,the IP may change when the PC is running ,i think this lead to the failure of network. but it cost much time to print error,makes me confusd.

thank you for your detail reply,Shanmugasivam Pillai!