Firebug swamped - it's time to arrange cleaning

Chanterelle got sick ... Firebug began to work very strangely, in particular, it stopped seeing styles for links and everything in them. At the same time, the HTML Validator died - always empty cache, nothing, they say, validate. Yes, and the cache itself began to behave extremely strange - before Fox was used as a ram to punch a very economical office proxy, now the pictures from the local Apache are cached so ironically that only clearing or disabling the cache helps.
The reason during the alternate disconnection of third-party extensions was found in the plugin DownloadHelper, recently updated to a new major version (3.0). It was worth immediately suspecting that something was wrong with such news - after disconnecting the unnecessary, in general, all my developer plugins started working like a clock!
UPD: Not so simple, we continue to investigate - my experience does not help the commentators