This might happen since Registry Booster 2 has a much improved scanning engine, that can find a high number of invalid entries.
However this does not mean that all the marked entries are serious registry problems, but they can merely be invalid shortcut links in your "recent documents" menu for example.
These are non critical errors, but they can still constitute an invalid registry entry, and you cannot deny that removing such invalid entries will result in a "cleaner" registry (and a smaller registry means a faster registry).
