On the affected Mac try this:
1. Go to System Preferences>Network.
2. In the Network pane look at the top of that pane for the 'Location' drop-down. Use that location drop-down to 'Edit Locations'. Use the + button to create a new custom named location (calling it whatever you want, just keep to one word).
3. Once a new custom Location is made rejoin your network and if every thing works click the 'apply' button to save this new custom Location. Don't worry because it will act the same as the 'Automatic' location.
Mac Pro Dual 2.8 Quad (2nd gen), 14G Ram, Two DVD-RW Drives, OS X 10.8.3
2006 Mac Book Pro 2.16 (first Gen) OS X 10.7.4
2TB Time Capsule, 2 TB
32G iPhone 4S Black, iPad (3rd Gen) 32G Black