The cache and cookies stored while using internet explorer can get corrupted especially when only the favorites are ever browsed.
To clear the cache and cookies;

1. Open internet explorer
2. Go to Tools > Internet Options
3. In the general tab click Delete files... then place a tick in Clear all offline content > click OK
4. Clik Delete Cookies... click OK to the prompt.
5. Click OK at the bottom of the internet options window to close it and save the changes.