MSN Drives Me Insane!

I have been working with optimizing Web sites for a while now.  I fully understand as much as one can in terms of how search engines work.  There is always the opportunity to learn more, reach out to the people who are more experienced, and study and test what entails making a site rank higher in search results.  However, lately, MSN is not making any sense to me at all.  I know that I have read that others have had similar issues with MSN, but it doesn't make sense to me that their results fluctuate so often.  For instance, when I was searching for one of my main keywords, gift cards, the results were varying on a daily basis.  Not to mention the site that was number one for a few short hours was not optimized at all.  Then, all of a sudden the results completely flipped and there GiftCards.com was back in the first natural position...unbelievable.  Many agree that MSN's is very different than Google's and Yahoo's, but I just don't understand the results fluctuating so frequently.