Linux Mint 10 Julia, based on Ubuntu 10.10 Maverick Meerkat, has been obsoleted since April this year. You would be recommended to install a newer version of Linux Mint. The current long-term support release is Linux Mint 13, with support till April 2017. The most recent release is Linux Mint 14, with support till April 2014. You can find all available downloads here: http://www.linuxmint.com/oldreleases.php
You are currently using the GNOME 2 edition of Linux Mint 10, I guess. GNOME 2 has been discontinued by the GNOME developers. Your obvious alternatives on Linux MInt 13 and 14 are MATE and Cinnamon. MATE is a fork of GNOME 2, so it looks very familiar. Cinnamon is developed by the Linux Mint developers and it is based on GNOME 3, so based on modern technology, but implementing the classic desktop paradigm as familiar from GNOME 2.
It may be that this functionality isn't working the same on your version of Linux Mint. Since it has been obsoleted, I don't have it installed here any longer so not sure how to help you on this. If you don't want to install a newer version of Linux Mint, perhaps fuse-zip program is an option: https://code.google.com/p/fuse-zip/