Post a link to your active site here so we could diagnose.
OK, it's available at http://www.pebmac.com/temp/
Try rolling over About Us and you'll see that the text above it changes. But when you roll back off of the button, the text remains, as opposed to swapping back to the original blank image.
I'm assuming you'd have assigned behaviors for the Swap Image twice - once for the about image to change and second time for the top image to change. This makes DW create 2 instances of mouseover code and the mouseout code is replaced by the 2nd change to your Swap Image.
The ideal way of doing this is to select your trigger image that you want to activate SwapImage function. Add behavior > Swap Image > first choose a swap source for 'about'. Don't Click OK yet. Choose your 2nd image that you want to change - text, in our case. Select a swap source for this as well. Ensure Preload images and Restore on Mouseout are checked. Now, click OK.
Your task should be completed.
I've uploaded the correct version at http://www.forwardfocus.in/sandbox/testmouseover for you to view.
Another quick thing I wanted to point out to you: I see you've used complete slices to make your site. This is usually bad practice. Try not to slice your site fully, directly from Photoshop. Define your CSS and use HTML with individual elements to complete your site.
Thanks very much! I'll try doing it the way you suggested.
As for the slices, I'm planning to go back and rework it with more CSS functionality once I get more familiar with it—that was the quick and dirty version.