cache_clear_all() doesn't seem to work I have a block with a few CCK fields. In this block I have a link to an action that changes the value of the fields in that block.

The code is the following:

db_query("UPDATE {content_type_event} SET field_event_places_amount_value = field_event_places_amount_value - 1 WHERE nid=%d", $nid);
cache_clear_all();  


After reloading, the old value still appear. I have to manually clear the cache to see the current value.
Check which cache is relevant (e.g. cache_content, cache_views_data) for this content and clear this cache explicitly. If you call cache_clear_all() without parameters you "only" clear the page and block cache. Take a look at the code of cache_clear_all() to see the details.