I experience the exact same problem. My PC is running Windows XP Pro SP2 on a Intel Core Duo 1,73 GHz CPU.
During normal usage SmartFTP constantly uses 40-50% CPU (remember i'm using Dual Core, so this is around 100% of one of my cores). However, when i open ANY window from within SmartFTP, the usage drops to ~0% - even when i open the About dialog.
The symptoms are exactly the same no matter if SmartFTP is minimized or maximized.
I don't know if this can help, but i tried do some logging of the activities done by the process while using 50% CPU.
This screenshot shows 19 registry queries being done constantly over and over (watch the time for each query!):
The CLSID being reffered to is:
= SmartFTP Shell Namespace Extension
I hope this can help to solve the problem.
Anyway, thank you very much for the best FTP client