Pro Tools Freezing during playback

[erictalley523]

So I am new to the forum, but have been using pro tools for about a year. i recently had to reformat my system, and reinstalled PT, but when i open a project, it loads fine but won't playback. I hit spacebar, and the entire thing freezes up and I have to restart PT, only to have it do the same exact thing. It also happens with new projects as well as old ones. I have tried adjusting the playback engine settings, but nothing happens. I reinstalled PT and all of my drivers are current, and I am only running basic plugins that come with PT 8 originally. I updated from the digi site and still nothing. I have literally read a hundred posts, and have yet to find anything that helps. PLEASE HELP ME!

Running Sony Vaio, 3GB ram, external hard drive, mbox 2 mini. everything worked three days ago, something i should have changed from the original setup?