[ubuntu-za] Update error

[Dr. Johan P. Prinsloo]

Since one of the recent upgrades, I've been getting the following 
message that prevents me from running further upgrades:

An error occurred
The following details are provided:
E: Could not get lock /var/cache/apt/archives/lock - open (11: Resource 
temporarily unavailable)
E: Unable to lock the download directory

I cannot open the file or change the permissions, because I need to do 
that as root (sudo), which I'm rather careful with and in any case I 
would not know the command.
What I wcan I do about this?
Johan