Plesk login page keeps loading on Windows: Application SID does not match Conductor SID

Symptoms

1. Unable to login in Plesk. Login page is shown and after submitting credentials it keeps on loading.

2. The following events appear in Event Viewer > Windows Logs > Application:

   CONFIG_TEXT: Warning 8/12/2013 3:48:25 PM RestartManager 10010 None
   
   Application 'C:\\Program Files (x86)\\Parallels\\Plesk\\admin\\bin\\scheduled_backup.exe' (pid 6964) cannot be restarted - Application SID does not match Conductor SID..

   OR

   CONFIG_TEXT: Application 'C:\\Program Files (x86)\\Parallels\\Plesk\\admin\\bin\\php.exe' (pid 4316) cannot be restarted - Application SID does not match Conductor SID..

3. The following events appear in Event Viewer > Windows Logs > System:

   CONFIG_TEXT: **Error 8/5/2013 12:29:06 PM HttpEvent 15002 None**
   Unable to write to the log file u_extend9.log for site W3SVC0. Disk may be full. If this is a network path, make sure that network connectivity is not broken.
   
   Warning 8/11/2013 8:01:50 PM srv 2013 None
   The C: disk is at or near capacity. You may need to delete some files.

Cause

Hanged php.exe processes.

Resolution

1. Connect to the server using RDP.
2. Stop Plesk Management Service using Plesk Services Monitor;
3. Launch Command Prompt;

4. Kill hanged php.exe processes with CMD:

   C:\> taskkill /f /fi "imagename eq php.exe"
   SUCCESS: The process with PID 5276 has been terminated.
   SUCCESS: The process with PID 4220 has been terminated.
   SUCCESS: The process with PID 4316 has been terminated.