They can break blocks just fine. I'm using build 935 and I'm using the plugins runecraft, default permissions and default commands. Everything seems to be running fine except for that one problem.
I have this same problem... It's something from Default Commands, since it didn't happen until I installed it. I can't find how to fix it though.
Same problem and I was about to open up my server They can break the blocks and place blocks, but can't pick up blocks, if you do /op playername from console then they can pick up items
Noticed this is the top thread on google for this problem; i found out that it can be solved by going into the Config.yml file in the associated world and changing op_permissions to "false". hope that works.