Strange Climbing Bug

[Capricious]

Last night in the "Exploring the Dark" quest I experienced a strange bug when attempting to climb, both with a rope and a climbing hook. Typically my modifier is +8, but I was experiencing a modifier of -13. I was not carrying more than usual or wearing armor.

It might be worth noting that this happened after my PC briefly was webbed before entering the quest. A relog fixed it, but I thought it was worth noting here.

[Aefar]

I have had similar experience. It is not climbing bug, but dexterity bug. AC, climbing, everything is like if you had dex 3, but in your sheet you see dex alright. It happens rarely and relog fixes it.
 
One of possible causes: http://nwn.wikia.com/wiki/Entangle_(spell)

[Dredi]

It's the webbing, it's a known bug it sticks your dex at 3 even after the effect has ended. Relogging fixes it, it also impacts ac - which is a pain