album art reloaded every time I scroll.

itunes 11 / OSX 10.8.2

iTunes library is on a QNAP NAS Drive attached via gigabit ethernet.

400 albums and 50 tv shows songs and 50 movies.

The album art reloads every time I scroll or change between categories.

Most content is purchased via the iTunes store.

This appears worse in the versions of iTunes.

Is this normal behaviour or do I have some settings wrong? (checked cables are all 5e or above.)

Any advice is welcome.

Thanks