I’ve had the same problem as mentioned: after updating WP to 2.7, Twitter for WordPress (1.9.2) stopped working, even blocking the showing up of widgets in the admin panel.
With some trial and error I managed to get it working again. Don’t really understand what I did, but here is the piece of code that seems to do the trick:
define(‘MAGPIE_CACHE_AGE’, 240);
// define(‘MAGPIE_CACHE_ON’, false); //2.7 Cache Bug
define(‘MAGPIE_INPUT_ENCODING’, ‘UTF-8’);
works like a charm…