P: brush cursors not working on 2011 Mac/MacBook Air (OS X 10.7.x Lion)

You don't have to enter the serial number on the Adobe site.
Just launch the setup program on tour computer, it will ask you for the serial number. Then, it will ask for your Adobe's account (to register the license, I guess).

Another way to filter images using flags is to use the toolbar options in the Library module.



Press "G" for the Grid view in the Library module and then press "T" to toggle the Toolbar.

Press any of the flags in the tool bar [highlighted above] to turn them on/off and note the text description that appears briefly on the screen.

Using those flags in various on/off combinations it is possible to filter images in a wide variety of ways.

Thank you, I'd missed that option here.

Also could use the Metadata section, change a column to display "Keyword" and select "None".

Use the Library Filter bar, with the Text criterion Keywords Are Empty:

Is there a way to select all photos without keywords? I don't see a way to select all photos with keywords that would allow me to invert the selection and get those who don't have keywords.

Got it - thanks!

If you use the Attribute section and select the middle/empty flag (red circles), you'll filter on all the unflagged photos. 

And if you find yourself using a particular filter combo often, I'd suggest making it a preset, so you can just select it from the drop-down on the right. (blue circle)

Do the menu command Edit > Invert Selection.

Another way to select photos that aren't flagged is to use the Library Filter bar, selecting Attribute and then clicking on the Unflagged and Rejected icons:



Be careful -- those icons are poorly designed and it's hard to tell which ones are selected.

Since your problem is unrelated to MacOS 10.7 (aka this topic), you should create a new topic so we can narrow down the issues you are having with MacOS 10.10.