I have already posted this bug some time ago but I have found an explanation for this (focus on the address bar). But the bug is still appearing on PCManFM 1.1.0 and in my OpenBox configuration is no action defined for C-V. To be more precise:
If I'm copying a file or directory with CTRL + C and pasting it to another directory with CTRL + V sometimes nothing happens. But using the context menu for pasting is working fine in this case. The last time you have said the context menu and pasting with CTRL + V are using the same code but there is definitely something wrong.