Open Ubuntu Software Center, click 'Edit' then 'Software Sources...', then click the 'Download from' list, choose 'Other', then click the 'Select Best Server'. Now your computer will perform a series of 'ping' tests to determine which server is closest to you (in terms of time). Afterward the tests are complete, you should be able to update your computer.
Open Ubuntu Software Center, click 'Edit' then 'Software Sources...', then click the 'Download from' list, choose 'Other', then click the 'Select Best Server'. Now your computer will perform a series of 'ping' tests to determine which server is closest to you (in terms of time). Afterward the tests are complete, you should be able to update your computer.