Bukkit

What steps will reproduce the problem?
1.New users (who dont have build permissions) get on my server
2.They try to buy things from server shops
3.Nothing happens when they right click

What is the expected output? What do you see instead?
I expect the signs to take their money and give them their items, instead, nothing.

What version of the product are you using?
32

Do you have an error log of what happened?
It doesnt produce one

Please provide any additional information below.
Im using permissionsbukkit and vault. Users with build permissions can use shops successfully, but default users cant. Default users indeed have the duckshop.use.* node in their permissions, but do they need build permissions to use shops?

You need to give your users permission to right click blocks. I don't use PermissionsBukkit myself, so I'm afraid I can't help you there.