Answers:
necessitate profoundly more info to answer 'why'
what operating system are you using?
what trellis browser are you using?
what are you trying to download?
does it transpire when you try to download from other sites?
do you receive any error messages?
what open-handed of make friends are you on? home, institution, work?
what anti-virus, anti-spyware, and firewalls, if any, are you using?
some adjectives downloads to try:
trapeze artist reader from adobe.com
firefox from mozilla.com
you may know how to use firefox for pattern browsing and downloading until you bring this figure out :)