Many thanks for your constructive help. I'm a bit embarrassed about the title of this thread now! I think I will ditch Zone Alarm for the time being and see how I get on with Adaware. How much does it degrade performance? Well I suppose I should suck it and see.
---------- Post added at 15:39 ---------- Previous post was at 15:35 ----------
Amazing! After crawling all day so far, it has just leapt back up to 1.9 Mb/sec! What does this mean? Watch this space
So all I have left to fix is Firefox which ZA has disabled.