This will seem like overkill to some but but if you are also using Firefox then might I recommend uninstalling it, downloading the latest version and re-installing it afresh if you have been using it for a while. It does benefit from a good spring clean every few months (and you can find others online who say the same thing). It wouldn't be a surprise if the same applies to other internet browsers.
Save all your bookmarks, add-ons and other data using Mozbackup or something similar (rather than simply copying data from the Firefox folder in yourapplication data), and use a proper uninstaller such as Revo to remove ALL traces of Firefox before the re-insatllation (in Revo's case used the advanced level of uninstall). By doing a thorough removal rather than just using the standard uninstall you are effectively starting just as when you first installed Firefox. But of course you do need to save everything that you use in the browser and subsequently restore them, unless you're happy with starting completely anew.
I have just done this in the last hour for the first time in 3 months and it is noticeably that bit quicker than before (and it didn't seem that slow then).