here are the details

Changes since 5.2.11
Prompt to retry the connection if a connection failed event occurs.
Treat various forms of the local computer name as a local machine instead of a remote machine.
Changes since 5.2.10
Wizards cannot be run without a connection to the core client.
Changes since 5.2.9
Win: Fixes a BOINC Manager connection issue when the manager is waiting on a firewall for the all clear. This generally happens after a reboot.
Changes since 5.2.8
Win: Fixes the 'connection failed' message when another program is using the BOINC communication port.
Changes since 5.2.7
Localization updates.
Resolve many connection issues regarding passwords.
Mac: Fix a screensaver stutter while scrolling text.
Changes since 5.2.6
Localization updates.
Usability enhancements.
Fix a crash condition when connecting to a remote machine.
Fix for file handle usage on Linux/Mac which caused BOINC to run out of file handles.

http://boinc.berkeley.edu/download.php?platform=win&version=5.2.12&type=win_new

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5.2.13 is now out,

Changes since 5.2.12
Localization updates.
Network communication failure page added which describes basic ways to resolve common networking issues.
Fixed a timing issue where the manager would look for the password file before the client actually created one.

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