Horizon was working just fine until it wanted the 2.8.5 update an my computer will not install this update…running windows vista…very frustrating…
Same here I really hope they fix this 
There is nothing to be fixed. Uninstall the current version, download the new one from here and install it as you did originally.
You could do what, Chris said, or you could download from this link: https://www.horizonmb.com/client/v2/latest.php
yeah well i uninstalled it an reinstalled it an it still won’t update…i am so frustrated this really grinds me.
my computer won’t install frame work 3.5 either it errors out,
Try downloading .Net Framework from here http://www.microsoft.com/download/en/details.aspx?displaylang=en&id=21 and try cleaning it up with this link http://blogs.msdn.com/cfs-file.ashx/__key/CommunityServer-Components-PostAttachments/00-08-90-44-93/dotnetfx_5F00_cleanup_5F00_tool.zip