Underpowered

I've been trying to install a few mods with IMG tool 1.3, but everytime I try to add the new .dff and .txd files, a window pops up that says "I/O error 32", and the program freezes up. I have tried every solution I could find on the web, including changing all the files off of read-only. Please, any help will be appreciated. Thanks in advanced =).