I'm playing Rhiannon on my netbook. I'm in chapter 3, in the building with the padlacked door. I've taken the crowbar, moved the can of paint, and am using MaGtRo's w/t up to the point where I have to take the long hook from the rafters - but it won't go into my inventory. Then I tried opening the trapdoor with my crowbar, tried to take the ladder. It, too, won't go into inventory - I clicked on the long hook and the ladder, they came off the wall/rafter, but when I click on them again to put them into my inventory, they go right back where I got them from.

What gives? My inventory is full. Is my inventory too full?
How do I get them into my inventory so I can use them?

You can pick up as many items - the inventory will not be full.

As for the long hook and ladder - you have to know first where you are going to use them.

Long hook - Go to the short pier at the pond. Go to the end and click on a jug at center of the pond. Then try to get the long hook.

Ladder - Go to the right side of the house and be under the scaffolding.
Look up and click on the scaffold above you. Then you know you need a ladder.