Originally Posted by spasmo

Are you sure your bid is high enough for your ad to actually show up? The estimates can be misleading. Sometimes they indicate a certain number of clicks per day even when your bid is too low to make the bottom of the list.

You might try boosting your bid for a couple of minutes to see if your ad shows up. If it's a high cost keyword I'd keep a live tail on your logs grep'ing for google in case it lights and you start getting slammed in the wallet.