You can make changes to your re-list from Auctiva (title, a lower starting price, duration, add images, etc.) and still be eligible for the relist credit on eBay. Here's a link to some of eBay's tips for relisting:
http://cgi5.ebay.com/ws/eBayISAPI.dll?BetterSellerOf course, I'm sure there are some other guidelines that need to be followed to get the credit (for instance, you can't take an unsold listing and change it into a totally different one to get the credit.) If I find more info I will post it here....good luck!