prOphet, PR and your keyword rankings are 2 completely different things. Fluctuating from #5 to #10 in a day is not all that uncommon on Google. Fluctuations in rankings are the status quo with Google. PR is only updated once every quarter or so (the PR you see in the toolbar anyway). It’s also important for others reading this to know that there isn’t a great deal of correlation between PR and keyword rankings, there are many other factors at play and PR is only one of the factors that determines where you come up in Google’s results.