From PayPal:
PayPal and eBay are working together to make payments for eBay items even safer. Because we want both buyers and sellers to feel confident about sending and receiving payments through PayPal, we may temporarily hold payments for items sold on eBay.
Make sure to ship the item right away, so you'll have access to the funds sooner. We'll release the hold in 21 days unless you receive a dispute, claim, chargeback, or reversal on the transaction subject to the hold. We may release the hold earlier if either of the following occurs:
The buyer leaves you positive feedback on eBay. We confirm that the item was delivered.* We can confirm delivery if you ship the item with USPS, FedEx, or UPS and either use PayPal shipping labels or upload tracking information from the transaction details page. This applies to transactions within the United States. Additional hold period
If you receive a dispute, claim, chargeback, or reversal on the transaction subject to the hold, we may hold the payment until the problem is resolved.
Learn more about the PayPal policy for payments holds on eBay items.
* This applies to US domestic transactions that are shipped by USPS, FedEx, or UPS and either (i) use PayPal shipping labels to ship items or (ii) provide tracking information to PayPal.
KillJoy