PDF files changed to shortcuts by Archive Manager are not retrievable by Adobe Reader X. The files could be opened without any obstacle if an older version of Adobe or any other PDF viewer is used.
Protected Mode - new security feature of Adobe Reader X - has to be turned off. Protected Mode protects users' applications and data by limiting what malicious files can do and access. It seems it is taking files having the Reparse Point attribute set as a malicious file. Protected Mode is enabled by default.
If you are having the problem described above, simply disable protected mode manually in Adobe Reader by choosing Edit > Preferences > General tab and unchecking Enable Protected Mode on startup.