The error is just a message box saying
The update procedure failed. For more information check the log. Press OK to restore your system
In the 3cxupdater.log there is this
System.IO.IOException: The process cannot access the file 'C:\Program Files\3CX PhoneSystem\Bin\3CXEventLog.dll' because it is being used by another process.
at PhoneSystemUpdater.ProgressUpdater.UpdateFile(ZipInputStream& s, String filePath, String rollBackFile)
Windows 2008 x32 sp2