Step 1: Boot into the Recovery partition (hold down the Option key on startup).
Step 2: Select "Disk Utility" from the Menu bar and mount the combo installer image file .
Step 3: Choose "Terminal" from the Menu bar and run "installer -pkg /Volumes/Mac\ OS\ X\ 10.7.3\ Update\ Combo/MacOSXUpdCombo10.7.3.pkg -target /Volumes/Macintosh\ HD", making sure to change the target to reflect the startup volume’s name.
Step 4: Run "reboot", and providing everything has gone smoothly, you should be running Lion 10.7.3 bug-free!