Hi Jem
First, try simply restarting your computer. (It frequently fixes problems like yours).
If that doesn't work, we need to know which browser you're using. If it's Internet Explorer, and you insist upon sticking with it (WHY? WHY? WHY?), then all I can suggest is checking the Microsoft website to ensure that you've got the latest version (in the hope that update IE will fix the problem).
If you're not already using Firefox, it would probably be best to switch to it:
http://www.google.co....cial&client=firefox-a
If you're already using Firefox download it again (to ensure that you've got the latest version) and then re-install it. You don't need to to uninstall Firefox first and you won't lose any bookmarks or personal settings. (Re-installing Firefox, 'on top of itself', fixes nearly every problem that can occur with it).
Chris