Open Opera and then go to tools > preferences > advanced > browsing and then under the loading heading select Redraw instantly.
Open Tools>preferences>advanced> network and then select servername compilation and uncheck all the check boxes.
Go to Tools>preferences> advanced > history: and the under the heading "Check if cached page is updated on the server" select never for both cached images and documents.
Always use a theme which does not slow down opera , Many themes are found to have slow down opera and it is recommended to use the opera standard theme or the windows Native.Go to tools > appearance to change the theme back to normal.
Try disabling Images and various Multimedia contents to make pages load Faster. This also lowers the bandwidth. Go here to read about How to disable images in Opera.