Unfortunately, you have posted to the Tips & Tricks sub-forum. This is basically a repository for articles on how to do things in PrE and not for fixing problems. Our trusted MOD, Steve Grisetti, will probably move this post out to the main forum, where many more people will see it and be able to respond.
Now, glad that you have gotten things sorted out.
To see if we can help find out what happened, please tell us about your Projects.
Let's start with your source footage. Please tell us as much about it, as you can. Did you do a Capture from a miniDV tape camcorder via FireWire in PrE, or did you Import it from another source. If you need to gather details on the footage, the freeware utility, G-Spot, can give you all of the information. The more detail, the better. One important aspect would be were these muxed (Multiplexed, i.e. combined Audio and Video files), or was the Audio separate files? Also, did this loss of Audio happen with ALL Audio sources, or select ones?
Next, can you tell us about your Project's Preset - the one that you selected, when you did New Project?
Then, were you in Sceneline View Mode, or Timeline View Mode? When you "lost" your Audio, were you still able to see the Waveform Display for it, but just could not hear it, or were the Audio portions of your Clips physically gone from the Timeline? If they were shown, but without their Waveform Display, or were missing entirely, did they still appear in your Project Panel? Probably too late to check now, but from the Project Panel, I'd be curious to know what happened, when you Dbl-clicked on the Asset and played it in the Source Monitor.
Answers to those questions might help someone point to what happened. Though now, it might be too late to gather all clues.
At least the reinstall got you back to editing!
Good luck, and don't be surprised if your post gets moved out to the main forum,