There was a discussion of this about two weeks ago. If you are a infrequent seller and don't meet certain criteria paypal holds your funds for 21 days, or less if certain other criteria are met
(say using delivery confirmation, or early buyer feedback). I sold a bunch of stuff 3 weeks ago. And the funds were released at different intervals. The sale total didn't amount to much so
I didn't get worked up about it, but I can see where it would be a major problem for some.

If you use ebay shipping I believe paypal will release those funds immediately for all users.