I just downloaded reader 9.4.0 twice, once from the Adobe website and once from a thirdparty web site. On both installations file associations get completely hosed and no programs can be launched because "Adobe does not support that association" All desk top icons are changed to unknown (in my case the eared paper with the adobe symble in the center). Luckly that the control pannel was working so that I could uninstall which brought everything back to normal. I am running Vista SP2 with updates, Firefox 3.6.11, Comodo 5.0.16+++, and AVG 9.0.862. I see others are running without trouble so it must be something particular to my system... Anyone have any ideas?
I have seen this a couple of times here in the forum, last http://forums.adobe.com/thread/741664 - always on Vista and Windows 7.
I have never been able to figure out why and what is happening, so in these rare cases I always ended up suggesting to use an alternate PDF viewer; see the above topic for some specific recommendations.