I've tried what you've recomended and it didn't work for me.
this is how my ifconfig looks like:
[root@hosting network-scripts]# ifconfig
eth0 Link encap:Ethernet HWaddr 02:00:5CE:A7:98
inet addr:********* Bcast:********** Mask:255.255.255.0
inet6 addr: fe80::5cff:fede:a798/64 Scope:Link
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
RX packets:1430 errors:0 dropped:14 overruns:0 frame:0
TX packets:179 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:1000
RX bytes:117215 (114.4 KiB) TX bytes:29819 (29.1 KiB)

eth0:1 Link encap:Ethernet HWaddr 02:00:5CE:A7:98
inet addr:************ Bcast:*********** Mask:255.255.255.0
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1

lo Link encap:Local Loopback
inet addr:127.0.0.1 Mask:255.0.0.0
inet6 addr: ::1/128 Scope:Host
UP LOOPBACK RUNNING MTU:65536 Metric:1
RX packets:3963 errors:0 dropped:0 overruns:0 frame:0
TX packets:3963 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:0
RX bytes:514421 (502.3 KiB) TX bytes:514421 (502.3 KiB)

and I've tried this command: ifdown eth0; ifdown eth0:1; ifup eth0; ifup eth0:1
output:
Determining if ip address ********* is already in use for device eth0...
Determining if ip address ********* is already in use for device eth0...
RTNETLINK answers: File exists
RTNETLINK answers: File exists

Any other ideas? Thanks.

I found in another thread the problem can be caused by multiple gateways in the /etc/network/interfaces (i'm on ubuntu 14.04), I removed the second gateway, and it solved the problem for me.

Tnx for this post, it helped me to resolve the same error caused by qemu/libvirt. I made a bridge adapter for my vm's to use but kvm also creates a nat network adapter with a default gateway. I did not notice this issue after i rebooted months later.
Since i dont't use the nat network i disabled it in qemu and after that it works again.

Gr,
Ronald