For those who want to play on the server and don't want to wait for an official 1.4.5 build release [which probably won't come due to 1.4.6 and 1.5 around the corner], MultiMC is one option. It allows you to install Minecraft anywhere on your computer, also letting you make several instances of Minecraft that won't affect your main installation at all [this is good for those of use who use different mods for different situations, or to just have several versions of vanilla available]. It also has a downgrade feature. allowing you to downgrade 1.4.5 to 1.4.2 for example.
MultiMC