By picking up an shotten arrow you not only pick up one, you will pick up arrows until your inventory is full. The arrow doesn't gets picked up.

Thanks, someone else reported this and I found that it was a bug with CraftBukkit. It has been reported (and supposedly fixed). You can see the bug report here for more details: https://bukkit.atlassian.net/browse/BUKKIT-1351

thumup

This is working on CraftBukkit #2122