Hi, I'm having the same problem as the OP. I downloaded a new version a few weeks ago, thinking if I re-installed it, that might help, but no. Then today I backed up as you suggested to the previous poster, but I don't know how to edit my registry or what to do. I start SmartFTP and I get the initial little window that tells me my copy is old, but it's not, I just updated it, and also gives me the option to download, and has the Okay button, which I press. After that, I get the "Loading, please wait" noise from my computer but nothing happens.
Since all they normally tell you is to install you the latest version over and over again, what you need to do is what mb said right before your post. Delete the registry file. Go to the SmartFTP folder in your start>programs menu, then Tools, then Backup, hit Next and then click the button next to Reset and then Next. Hit next again and then unclick the first two tabs and hit Next and Next again. That should finish it off. This is the only thing that worked for me. "Install the latest version" is the answer you get anytime you ask a question but its not the full answer.