I was having this problem as well on my Hero and this is how I fixed it:
On the phone, open Settings > Applications > Manage Applications. Find Facebook and remove the update. Then find Facebook for HTC Sense and clear data.
On the phone, open Settings > Accounts and Sync > Facebook for HTC Sense. Remove account.
Log onto your facebook account from the computer and in the top right corner click on the Account drop-down menu. Choose Application Settings.
On the Application Settings page, go through each "Show" in the drop down and click the "X" whenever you see "Facebook for Android" or "HTC Sense".
I turned my phone off then on after that last step, bit I don't think it's necessary.
On the phone, open Settings > Accounts and Sync and choose add account. Choose Facebook for HTC Sense and put in your user id/password.
DO NOTHING! Don't log in to the Facebook app. Eventually, my contact's began to sync in the people app, but it took a long while. Finally, most of them synced, but I had to manually sync a couple (which I couldn't even do before).
After they synced, I logged into the Facebook app, but have yet to install the latest Facebook update.
Hope this helps. I found these suggested steps on the HTC Sense Facebook discussion boards. Apparently, like Will says, it's happening to a lot of android phones right now.