MS updates has encouraged update from IE6 to IE7. Have taken that recommendation to mean that IE7 is now fully mature and fit to be released to the general public. However, despite a number of reinstalls, IE7 refuses to open PDF WebPages or PDF attachments embedded within WebPages. This is a rather fundamental and much missed attribute. How does one change IE7 settings to open PDF documents ?
Assuming that you use Acrobat Reader, in Acrobat Reader you could try going into Edit, Preferences and select the Internet category and toggle the Display PDF in Browser off and on and see if this re-syncs OK.
When you install Adobe, it automatically installs certain files within I.E. so that it can work with it. If you update or alter I.E., this action will remove these files, therefore, you will have to re-install Adobe so as to replace these files in I.E.