There is a thread at WebmasterWorld and several in the Google Analytics Help forum with complaints that Google Analytics is no longer tracking Google AdWords data properly.

The WebmasterWorld thread has this complaint:

The simple answer is that in February, Google notified us that we need to link our analytics account to our AdWords accounts to pass this information. So if you have not done so, and your Analytics data is looking a bit empty, go ahead and link up those accounts. Brad has a good post explaining how to link up your accounts.

Forum discussion at WebmasterWorld and Google Analytics Help.