I think zeroOevolution has the problem I have: When I shut down my pc I leave open all the tabs I might need next time. When Opera restarts next time I have it set to open with the same tabs as last session. But instead of loading the cached pages, it downloads them all again. The trouble is - that takes ages, specially if some of them are no longer valid.
In Firefox you can avoid this. Lately I have problems with Firefox, so I have shifted to Opera which is usually faster.