Regarding the MAX_ALLOC_PERCENT environment variable:
This setting is CASE SENSITIVE! I got stuck on this for a while. Go to your Environment Variables Settings panel:
Click the Start Button
In the search box type "var" without quotes.
Choose the "Edit the system environmental variables" option.
Click on [Environment Variables...]
Verify that MAX_ALLOC_PERCENT is present in ALL CAPS with a value of 100.
This will allow you to increase the thread-concurrency.
Wow, I can't believe it was something as simple as that! I have literally tried everything I can think of to figure out why the hell I couldn't get any thread concurrency above 8192 to work in cgminer. You are the man! What's your LTC address? I'm gonna send you some.