We've had two users with this issue now. The Sent Items folder only shows mail from 2007 and earlier. Occasionally it will show items from the same day but usually not. If you right click on the folder and go to Properties and then click the Contains button it will show the proper count.

Interestingly enough, if you go to a different folder and then back to Sent Items over and over you'll eventually see all the items. But then switch back again and it's the same.

Of note is that there are a huge amount of Sent Items (upwards of 50-70K). I've also restored display settings to defaults for the folder and made sure there was no filter on.

Any thoughts?