chris is on the nail - surprised it hasn't worked
I always go for the every visit option ... with BBand it takes no extra time.
try emptying the temp folder
(tools | options)
try increasing the cache to <300Mb (don't go mad - 350-400 tops) - the bbc is a big bulky site
(i've used up to 800 on some company sites running sales databases).
ccleaner is a good general "housekeeper"
http://www.ccleaner.com/download
check your disk for errors and defrag once in a while
none of this may actually be the cause ... but if your system is more than a few months old - it's surprising how the rubbish mounts