This is frustrating. I recommend Apple products to students on the basis of their excellent accessibility. So, this particular bug is a problem for many.I hope it is fixed soon.
Meanwhile, I have a workaround that is not ideal, but better than nothing.
1) CREATE A SERVICE TO SPEAK HIGHLIGHTED TEXT
open Automator, chose FILE>NEW>SERVICE
select and double-click Speak Text from the Actions sidebar menu
SAVE and name it something memorable (e.g. "Alex Speaks")
QUIT
If you highlight text in any program, you can now have it speak to you by running this Service app. Simply highlight some text in any program, and right-click (or control click) to find "Alex Speaks" and click it. (Alternatively, you can excute it from the Services menu in the dropdown menu next to the apple symbol on the menubar at the top of your screen.)
2) CREATE A HOT KEY FOR THE SERVICE
go to System References
open Keyboard
click Keyboard Shortcuts
in the left-hand panel click Services
scroll down in the right-hand panel until you find “Alex Speaks"
double click on whitespace on at the extreme right hand end of the line that says "Alex Speaks"
type a key combination for the hotkey (make sure you choose something unusual).
make sure the check box next to “Alex Speaks” is selected
That's it! Now, if you select text in any application, and hit the hotkey for “Alex Speaks” the selected text will be read aloud, much like it did before Lion.
N.B.: This workaround is not as good as the real thing. First of all, the Service will not run via the hot key unless it is loaded into memory by selecting the service from the contextual menu first. Tthis has to be done for each application. secondly, once it starts reading it won't stop until it finishes the selection. This simple Automator app does not toggle off. Lastly, if it encounters a problem it may fail to work again unless you reboot.
Apple–please fix this!