Invalid checksum indicates that the download got corrupt during downloading. You might need to redownload.
Could you also give us some details about your computer and your internet connection, that'll help folks figure out if something else might be incorrect.
If you are receiving the message that the download is extracting then it has not completed the download process. Where are you choosing to download the install files too? It is likely the Adobe Download Assistant does not have sufficient permissions to save to that location.
I got it to work. I had to go into my utilities and uncheck the checksum box in order to retrieve the information.
Thanks for the response,
Excellent in the future please choose the default of your User folder to download the install files too.