Hi, I'm having what i believe to be the same issue. I have Modloader. Hope thats not the problem. Inventory Tweaks Forge. Rei Minimap and Optifine HD B3 I noticed the ladders immediately, but out of curiosity, jumped into creative, and have the same problem with Trapdoors and Vines (Cant Climb) I have them installed via Magic Launcher, with all Internal except Inventory Tweaks. Hope thats enough information, hope you can help.