If you have a decent Internet connection and you are downloading at high speeds, it may be possible that the disk gets overloaded. That means that the buffer is filled and you will experience slow responding times to computer and hard disk activity. Also, check the system requirements of the application because if it's built on the Java technology, it will consume many resources regarding RAM and CPU.
From what it seems, the application is actually a browser with built-in torrent capability. Please update it to the last version in order to eliminate bugs or any other memory leaks because this also is a possibility regarding functionality of the software.