Is it a bug? Here is a response from zynga tech support about this “expired gift” problem:
We are in the process of changing our gift process to work with the changes on Facebook.
You may see there are some changes to limits, and uncollected gifts will now expire after 30 days.Make sure to accept your gifts regularly from the Requests section on Facebook.
If you have received a message stating a gift was over 30 days old incorrectly, please send us the name of the gift which gave you the message.