Thread:Extension talk:DumpHTML/Error: Unable to copy file/reply (7)

I don't know what version of DumpHTML (if any) will work with MediaWiki 1.18.2. Your best bet is to try it with the current MediaWiki version (1.21). If it still doesn't work with 1.21, you'll probably have to debug it yourself. Patches to fix any issue are of course highly appreciated!