Bug in Gigapixel upgrade

I have just loaded the upgrade of Gigapixel. A programme that has worked perfectly for 2+ years now crashes every time I try and re-size a photo. As well as that as soon as I click to open the programme my computer grinds to a virtaul halt. How do I get rid of the upgrade and go back to what I had 5 days ago

If you want to roll back you can find previous versions here Product Releases - Topaz Discussion Forum