PokerTracker

I did the housekeeping and since then PT4 no longer works, it's become extremely slow, unusable while I'm playing, the hud no longer displays, it's even made a site I'm playing on disappear.

In PokerTracker 4 click 'Database -> Database Management', click your database then 'Rebuild Cache -> Full Cache Rebuild'. If that does not fix it then please turn on 'Enable Logging' in PokerTracker 4 via 'Configure -> Options', restart PokerTracker 4 and reproduce this problem you are describing. Next create a support bundle via the 'File -> Create Support Bundle' menu option in PokerTracker 4 and then attach that to a Support Ticket where a technician can review your logs and advise you accordingly.