|I suggest that this is **not** and Adobe problem, but a problem with the browser or system settings. Possibly even a system registry problem. When the Reader is installed, by default, it sets the PDF file association to launch the Reader. If this association is getting corrupted, replaced or removed, then the automatic launching of the Reader will fail.|
I don't remember if you are using Firefox or Internet Explorer. Or some "branded" version of a browser like the AOL browser. You may need to check on things like your security level, whether or not the appropriate plug-in is installed. (IE doesn't need an Adobe Reader plugin, but does require a file association for files with PDF extensions.)
Of course, the question remains, what transpired on your system since the last time it worked correctly? Was anything installed? Did you visit any websites that launch any Active-X scripts?
Have your run HiJackThis? If not, download it and run it. BE VERY CAREFUL with this tool. If you don't know what you're looking at, you can easily destroy your system with a corrupted registry.