That's a little outside the scope of this forum (there may be an installer forum -I'd have to check) but in your shoes I would:
Use a different browser.
Enable cookies for Adobe.com (and any third party cookie for Akamai, etc., if prompted)
Enable scripts and be sure Java is up to date on your system.
It would help to know your OS, Browser, and what the error message says, exactly.
I am posting on this topic because I have the same problem.
When I launch Adobe Download Assistant to install the trial version of InDesign CS5.5, I receive the Error 100 message.
I have tried every steps of solution 1 but nothing works.
My OS is Windows 7 ; 64 bits.
I have also downloaded Adobe AIR and the last version of Java for both windows 64 bits and 32 bits.
I start getting desperate because I really need this software so if anyone can help, it would be really nice !
Sorry if my English is not perfect, I am not a native English speaker.
Thanks a lot !