clear the history and the chace trought the combo Ctrl+Maiusc+Canc.

Try to clear/delete the cache folder manually, see about:cache for the location.

The default maximum size for the cache folder should be 256 MB in current Firefox versions (pref: browser.cache.disk.capacity), although there are more cache, so you may want to check the value of this pref and reset/change if necessary.

• Tools > Options > Advanced > Network > Cached Web Content

• http://kb.mozillazine.org/about:config

Here's the thing. I don't want to have to keep emptying my cache, I'd like to keep it at a manageable size. I just lowered Tools > Options > Advanced > Network > Cached Web Content to 250mb. it was set at 1024mb but it consistently exceeds that limit.
These are my config settings
browser.cache.disk.capacity;262144
browser.cache.disk.enable;true
browser.cache.disk.max_entry_size;51200
browser.cache.disk.smart_size.enabled;false
browser.cache.disk.smart_size.first_run;false
browser.cache.disk.smart_size.use_old_max;false
browser.cache.disk.smart_size_cached_value;358400
browser.cache.disk_cache_ssl;true
browser.cache.memory.enable;true
browser.cache.memory.max_entry_size;5120
browser.cache.offline.capacity;512000
browser.cache.offline.enable;true
These are default settings, will modifying these solve my problem?
or is something else going on?