When you upgrade your Mac OSX from Leoprad to Snow Leopard, you are bound to encounter compatibility issues among your various applications. There is virtually no tool in Snow Leopard that can give you a report on whether such applications will work or not. But a separate program called Snow Checker does the trick.
Choose to have the program list all programs or just the 3rd party applications that you installed in your system and it will simply display all applications including its status whether it is compatible or not. This software is free by the way so give it a download.