Perhaps you've installed the Multilingual User Interface (MUI) version of Adobe Reader but you've only published the update for the standard version "Adobe Reader XI (11.0.21)" and haven't published "Adobe Reader MUI 11.0.21"? Or vice versa?
If that's not the issue, let us know which version of Adobe Reader XI is currently installed.
So we currently have 11.0.11 (Standard version) that install's during the task sequence. I had published the 11.0.22 (standard version) back in September when it was released. It was working up until this month. I tried to re-publish it last night to see if it would go out, but I didn't see it show up. I also published out Java updates and those showed up just fine. Not sure if there is a log file that i should be checking out to see whats going on.
Update: This might be too big of a jump going from 11 - 22. Manually tried to upgrade .11 to .22 and it failed.
Ah yes, that's the issue. 11.0.22 is an out-of-cycle hotfix so it would require 11.0.21 to be installed first.
I will point out that you can include the patches in the installer. See the Enterprise Administration Guide for details.
Also, are you aware that Reader 11 reached end of life four days ago?