I'm deep in act 2 (rebuilding the keep) and now suddenly my party refuses to move unless I direct them to talk to someone, enter a building or transition to another area. The cursor also doesn't change when I try to click on the ground (it remains a pointer arrow, doesn't become a blue circle). On top of this, the character animation has become juddery and the status above the characters (power attack mode activated) also 'shudders'.

Anyone encounter this bug as well and know what to do about it?

Character stutter is a known problem. See my post here:
https://www.gog.com/forum/neverwinter_nights_series/disc_version_gog_and_the_stuttering_movement_bug/post14

That should fix stutter. You may find everything works better after that...

I added the .dll but unfortunately it did nothing. The main problem is that I can't click on the ground any longer to tell the party to move. The arrow just stays an arrow, the blue circle doesn't appear. So unless there's an NPC or item around which can be interacted with in range, nobody moves anymore. This affects every character. Also, the camera is no longer free, though I set it to be. It stays with the characters.
This bug has affected my earlier saves as well. i'll have to start over completely if I don't find a fix...
Incredible that this game, enjoyable as it is, is still this buggy after all these years.