This is a known issue after upgrade to SP1 the SCCM 2012, and to solve it, we just need to change something in the Boot Images and update on the DP´s.
Just follow the next steps:
- In the Configuration Manager console, in the navigation pane, click Software Library;
- In the Software Library workspace, go to Operating Systems;
- Click on Boot Images;
- Right-click a Boot Image and click Properties;
- On the Customization tab, check or uncheck the Enable command support (testing only);
- Click Apply and Yes in Do you want Configuration Manager to update the
distribution points now?;
- The Update Distribution Point Wizard will popup. In the Summary page click Next
- In the Completion page click Close.
Now you can test the PXE Boot