Is it an item in a category that you have not sold before? or possible a designer label item? That happened to me when I started selling designer handbags like Coach - because there are so many fakes out there, paypal can take a little longer to release your funds.
Copied from Ebay:
"Yes, you could still be subject to having funds show as pending for a period of time if your account doesn’t meet the minimum performance standard required of all eBay sellers. There may be other PayPal policies that also impact the availability of funds if a higher than normal level of risk is associated with your account—for example a sudden spike in eBay Buyer Protection cases, PayPal disputes or claims, unusual selling activity, items with an exceptionally high selling price, or sales in a NEW CATAGORY or a category such as tickets, travel, or gift certificates"