What browser are you using?
Internet Explorer? Firefox? Safari?
If you are using Internet Explorer 8, there are some quirky issues with this version.
Can you try another workstation?
Can you try a different browser?
Are you actually downloading this file and then the problem is with your Adobe Acrobat Reader?
What version of Adobe Acrobat Reader? Try a different machine with a later version, etc...
Saving one egg, cat and butterfly at a time