In my testing of AR X on Windows 7, I noted the Protected Mode error that has been posted in these forums many times before.
Notably, the problem did not show when logged in user a local admin account but did occur with a network admin account.
I found that changing all network references in HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Explorer\User Shell Folders to local references, stopped the protected mode error from appearing when logged in as a network admin.
So, in our case at least, the Protected Mode error appears to arise whenever the user shell folders are redirected to a network share.
Hopefully this may help others trying to get this software working.
Thanks for posting.
We have had a few bug reports related to Adobe Reader X protected mode coming in from users in this forum. We have addressed a large number of them in our upcoming Reader update and we would like to hear your feedback.
To that extent, we would like to invite you to the Adobe Reader Prerelease program and try out the latest build. To participate, please fill in the form available at https://www.adobe.com/cfusion/mmform/index.cfm?name=reader_prerelease_interest and indicate Adobe Reader as the product of your interest.
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Adobe Prerelease Team