Lack of free space? just type in

du -sk *|sort -n

on /

or any folder you like. You will get an information about space occupation where you can investigate further.

Sample output:

0 fastboot
0 proc
0 sys
4 boot
4 dev
4 lib64
4 media
4 mnt
4 srv
8 aquota.user
8 home
12 aquota.group
16 lost+found
120 tmp
644 run
6080 bin
7244 sbin
8544 etc
29076 lib
1345892 opt
1364796 usr
3028736 root
12280360 var