UIImage:imageWithContentsOfFile is 10 times slower in iOS 5.0

After simply recompiling our iPhone application on newly released iOS 5.0 SDK i faced strange problem - all UIImage:imageNamed (first call with actual image loading) and UIImage:imageWithContentsOfFile started to work 10 times slower than before. i managed to narrow problem down: this is the case only for jpeg and png files (not gifs!) and this is not because of file size. even straightforward loading of small 32*32 png takes around 300ms... compared to 30ms on older devices (checked on 3.1 and 4.3.5 with the exact same code)After simply recompiling our iPhone application