This problem also seems to affect languages other than Latin (Japanese, Chinese, Greek etc.).
If a Windows user name (and its folder name too) contains Cyrillic characters, they are not recognized correctly when updating Acrobat Reader. In some cases, this may result in a folder named "????????" being created in the C:\Users folder.
You can track this issue with the help of Process Monitor (procmon.exe)

Steps:
1) Create a Windows user with a Cyrillic name or use a Russian-language Windows distribution and activate the built-in Administrator account (which always has a name in the language that corresponds to the Windows language).
2) Install Acrobat Reader
3) Run Procmon.exe, select the filter for the RdrCEF.exe process.
4) Run Adobe reader update task from Task Scheduler or run C:\Program Files (x86)\Common Files\Adobe\ARM\1.0\AdobeARM.exe.
5) In procmon.exe, you will see attempts to create the C:\Users\??????\AppData\Local\Adobe\AcroCef folder that will succeed or fail depending on the permissions on C:\Users. (see screenshot)