A common problem after upgrading a kernel via yum on Centos is not creating the new kernel modules.
An example of this error happens when you try to use grep as in the print below.

# iptables-L-n | grep "my ip"

FATAL: Could not load/lib/modules/2.6.32-042stab123.9/modules.dep: No such file or directory

#

This indicates that the directory 2.6.32-042stab 123.9 and therefore any module in your content can be loaded.
To correct this problem, the simplest way is this recipe:

# mkdir -p /lib/modules/uname -r

# cd /lib/modules/uname -r

[root@vps3 2.6.32-042stab123.9]# depmod

[root@vps3 2.6.32-042stab123.9]# ls -lah

total 64K

drwxr-xr-x  2 root root 4.0K Oct 18 16:11 .

dr-xr-xr-x 10 root root 4.0K Oct 18 16:11 ..

-rw-r--r--  1 root root   45 Oct 18 16:11 modules.alias

-rw-r--r--  1 root root   12 Oct 18 16:11 modules.alias.bin

-rw-r--r--  1 root root   69 Oct 18 16:11 modules.ccwmap

-rw-r--r--  1 root root    0 Oct 18 16:11 modules.dep

-rw-r--r--  1 root root   12 Oct 18 16:11 modules.dep.bin

-rw-r--r--  1 root root   73 Oct 18 16:11 modules.ieee1394map

-rw-r--r--  1 root root  141 Oct 18 16:11 modules.inputmap

-rw-r--r--  1 root root   81 Oct 18 16:11 modules.isapnpmap

-rw-r--r--  1 root root   74 Oct 18 16:11 modules.ofmap

-rw-r--r--  1 root root   99 Oct 18 16:11 modules.pcimap

-rw-r--r--  1 root root   43 Oct 18 16:11 modules.seriomap

-rw-r--r--  1 root root  131 Oct 18 16:11 modules.softdep

-rw-r--r--  1 root root   49 Oct 18 16:11 modules.symbols

-rw-r--r--  1 root root   12 Oct 18 16:11 modules.symbols.bin

-rw-r--r--  1 root root  189 Oct 18 16:11 modules. usbmap

[root@vps3 2.6.32-042stab123.9]# iptables-L-n | grep "my ip"

[root@vps3 2.6.32-042stab123.9]#

This will create the directory and dependencies to modules for the kernel currently in use (uname -r).
If the problem is not resolved with the above commands. Try to reinstall the kernel via yum with the commands below.
mv /boot/grub/grub.conf /boot/grub/grub.conf.bak yum -y reinstall kernel
And then try the commands listed earlier.
I hope you find it useful both when it was for me.