From a little research this is what I am getting:
"1) Delete the value, not the key, of HKLM\Services\PTT\Dll (was "PTTService.dll", will now be "") and soft reset.
2) Run AE Button Plus, add the PTT button as a new key, and set its action."
AE Button Plus has a free trialware if you do not have it already, just run it in a search engine. Hopefully this works out for you, repost if there is a problem and we'll find a different route, or hold out until we get some more suggestions in here.