Extended trading leaned to the negative side on Thursday thanks in part to a falling Apple ( AAPL), which was one of the most heavily traded stocks after the bell on its announcement of a major product delay .

The California-based computer giant said its new Leopard operating system won't be released until October -- at least three months after it had originally planned -- as a consequence of diverting resources to ensuring the timely release of its iPhone product. Shares were recently sinking $2.39, or 2.6%, to $89.80.

Another highly active stock after hours was Dyax ( DYAX), a biotech that catapulted 48% amidst positive late-phase preliminary results for DX-88, a proposed treatment for acute swelling and inflammation caused by hereditary angioedema. The study achieved all primary and secondary endpoints. Shares surged $1.92 to $5.92.

Meanwhile, North Carolina's Krispy Kreme Doughnuts ( KKD) slid 5% to $10.73 after posting a fiscal fourth-quarter loss of 39 cents a share on sales that dropped 8.2% to $112.2 million -- $11 million under the only analyst estimate from Thomson Financial.

California-based Varian Medical Systems ( VAR), which focuses on cancer therapies, sank 5.7% to $46.14 after estimating only a 7% sales rise in the second fiscal quarter from last year -- about $442.9 million, roughly $11.4 million below Street targets.

Elsewhere, small-cap protective-garment maker Lakeland Industries ( LAKE) saw a 6-cent per-share drop from last year to 24 cents in the quarter ended Jan. 31, scaring shares down 9.7% to $13 in recent after-hours action.