When Registry Booster fixes all the errors it will ask you to restart. After doing so certain programs running in the background might re-create some of the invalid entries removed and thus registry booster will re-detect them as errors.
This will result in a number of errors being fixed the first time Registry Booster is run, but a small number of errors might keep reappearing after each reboot.
In order to eliminate these errors once and for all, you need to find which program is responsible for re-creating these registry entries, however you should not bother too much if the number of errors is minimal.