I've been finding some kw's where Max CPC is being constantly overpassed.
Jotafk, I've actually heard this concern dozens of times in the past, and in every case it turned out to be a matter of looking at one's stats for a 'date range' that included a time when the Max CPC was indeed higher that it is currently.
So be sure to double check your date range setting. It is a 'sticky setting' that stays where you last put it, which can create a little confusion for advertisers who assume that it defaults to the current day, or some other setting.
If this issue turns out not to be related to the date range setting, then I think your best bet would be to contact AdWords Support, and have them take a look at your account in detail.
jotafk, if you're not sure whether you have changed the max cpc or not, you can use the new "My Change History" feature found in the Tools section to confirm that. This is really a cool feature that tracks very bit of changes you've made in your account.