After researching this issue I have discovered that a number of remote access software suppliers have had this problem AFTER the upgrade from Lion 10.7.3 to 10.7.4. That recent upgrade has something in it which corrupts the screen sleep settings for future wake-up activations.
That is, once I have set my screen sleep to xx minutes before sleep activation, it will wake only on the first attempt from a remote user AND after that connection, the screen will sleep again as set BUT will never wake again when contacted from a remote user.
Apple has offered many solutions, all aimed at other functions and settings. After 90 minutes on the phone with Apple, trying all of their suggestions, nothing worked.
Then, after contacting a remote desktop developed and being told that their research indicated the fault is in the Lion 10.7.4 upgrade and that Apple as indicated to them that they will not be addressing the quirk in the future.
The workaround appears to be this:
Set screen sleep preferences to "Never Sleep" and use a screen saver to dim the screen leaving the computer open to receiving remote entry. It works. I chose the darkest, most minimal scree saver which starts after my setting of three minutes. It wakes when remote access is attempted.
The software developers are trying to find a way to fix this because Apple says they aren't going to make changes to address the upgrade-induced glitch.
Timbuktu (Motorola) is my software and they don't know what the solution is and are offering simple re-install solutions, which of course, don't do anything to address the issue.
One other company, GoToMyPC has their engineers working on a solution for their software to address this issue.
I'm finished being the commando on this issue and hope someone will advise Motorola that they are not addressing this issue with their current level of understanding of the problem.
Good luck
---Gary