I fixed it myself.
Go into the 'Program Files' folder in the C drive( Go to 'Computer', then 'C:', then 'Program Files' ):
-right click the 'Maxis' folder
-click 'Properties', click the 'Sharing' tab
-click 'Advanced Sharing...'
-check the box next to 'Share this folder'
-click 'Permissions'
-highlight 'Everyone'
-check the box next to 'Full Control' under the 'Allow' section
-click 'ok', click 'ok' again, and then click 'close'.
You're done!
It should be able to update properly after that.