I did a quick google and there was mention here that NWN does not like multiple processors, and setting the CPU Affinity in nwnplayer.ini should fix it.
[Game Options]Client CPU Affinity=1
It did not fix the issue for me, so I had another look. Now my dv6 comes with Switchable Graphics - which is a feature where the laptop has both Intel Graphics and the Radeon HD 6490M, and can automatically switch between the two for different applications in order to save power and avoid heat.
Naturally I had checked that my Catalyst Control Center had Neverwinter Nights set for "High Performance" GPU when trying to play the game. However I noticed that when I used Neverwinter Night's graphics configuration utility, it initially complained about not finding the appropriate drivers. I dug deeper and found this issue: OpenGL Applications Cannot Use Discrete GPU with Intel + AMD Switchable Graphics
This issue affects a range of HP laptops with switchable graphics, including the Pavilion dv6/dv7/g4/g6 and the new ENVY series. The fix was surprisingly easy (documented in the link above). I had to go into my laptop BIOS and switch the Switchable Graphics mode from Dynamic to Static, which meant only one graphics card would be active at any time (instead of splitting graphics card usage by application), and then go into "High Performance GPU" mode whenever I wanted to play Neverwinter Nights.