Firefox won't open after CCleaner run

Lately (i.e., new problem) after I run CCleaner, Firefox won't open for some time...and then will finally open. What do I need to do so this won't happen?

Thanks in advance.

Can you give a bit more info such as your operating system, build of ccleaner used, and if you are cleaning the registry (issues)

When you say FF won't open for sometime, what exactly happen?