Ok, so at the top of the IE page there drop down lists for File, Edit, View, Favourites, Tools and Help
Click on Tools
Go to the bottom of the drop down list and select Internet Options
The Internet Options box will open and you'll be on the General tab
On that tab there is a section called Browsing History with 2 buttons, Delete.... and Settings
Click the Delete... button and another box will open up
You can choose to individually delete the different things with the buttons on the right or use the Delete all button at the bottom to clear everything. The key things to clear in this case are Temporary Internet Files and Cookies but I'd recommend using the Delete all button (unless you need to keep your browsing history or auto passwords if you have any you won't be able to remember).
When you click Delete all you should see another box asking if your sure...click Yes
A box with a progress bar will appear while it deletes everything from the cache
Once it's done, click on OK in the Internet Options box to make that go away.
Finally close you browser, then restart it and come to the forum to see if the buttons have reappeared