So, if you read the full thread, you might have picked up on some of the information that would be helpful in figuring out what the problem is.
If you didn't receive an error during the actual installation, then the download you have is good, and you do NOT need to keep downloading it to reinstall it. Use the download you have. And back that up to a DVD, labelled including the install key so you don't lose it.
Please tell us about your computer, how fast is the processor? How much memory (RAM) does it have? How much hard drive space does it have?
What format are you capturing to?
At what point do you receive the error, during the actual capture, or during a conversion step, when you first start the program? Is there any consistency to when you receive the error, such as, after "x" number of minutes? What are you capturing from, a VHS player?
Any and all details can help us help you figure out what the problem is.