Update: Failed to lock /var/cache/apt/archives/lock

I am running the upgrade(12.10 to 13.04) through terminal and it keeps getting stuck at this:

Failed to lock /var/cache/apt/archives/lock

What do I do? I have root access. I have no idea what else to try other than a clean install.

Checking package manager
Reading package lists... Done    
Building dependency tree          
Reading state information... Done
Building data structures... Done 

Calculating the changes
Calculating the changes

Do you want to start the upgrade? 

3 packages are going to be removed. 155 new packages are going to be 
installed. 1204 packages are going to be upgraded. 

You have to download a total of 595 M. This download will take about 
1 hour 15 minutes with a 1Mbit DSL connection and about 23 hours with 
a 56k modem. 

Fetching and installing the upgrade can take several hours. Once the 
download has finished, the process cannot be canceled. 

 Continue [yN]  Details [d]y

Fetching

Could not download the upgrades 

The upgrade has aborted. Please check your Internet connection or 
installation media and try again. All files downloaded so far have 
been kept. 

Failed to lock /var/cache/apt/archives/lock 


Restoring original system state

Aborting
Reading package lists... Done    
Building dependency tree          
Reading state information... Done
Building data structures... Done 
root@chaitanya-XPS-Ubuntu:~# 

I had this happen. Its because you have a package manager open. See if you have synaptic, or other apt open, and close it. Also if you have GUI update manager running at the same time it will give you that same error.