Hi:
I know that is unrelated cache memory (for basics of running an OS), but they have cleared the cache ?, since entering a site, the browser should look for if you have previous information on the site and rescue, if so necessary, the cached information, which is disk access, and this is generally slower than RAM access.
The second is to see that your OS is clean and processes also are optimal, since usually shooting against the browser, but sometimes we have processes (call MSN or Skype or whatever) that occupy a large portion of our RAM, using virtual memory (or swap in Linux), which is writing data to disk, and as I said, is slow.
Suggest, either, to see the resources they occupy and if they have RAM to run ... and above all, keep the updated browser as Chrome 6 for quite a while longer the last;)
Regards