Hi JaToLe,

first, I wouldtry to reset WCF:

The following procedure recreates the database-templates of WinCC flexible and erases the caches:

1. Please close all processes „Hmies.exe“ and „HmiSmartStart.exe“ with the Windows TaskManager. Please do not close the TaskManager.

2. After this please start the following procedure (described below) via START > RUN and copy following line into the command prompt (maybe you must adapt your install path to this command line):

"C:\Program Files\Siemens\SIMATIC WinCC flexible\WinCC flexible 200x\Hmies.exe" -reset -new -silentmode true -autoclose true

3. After this you must check the starting of a new task hmies.exe in the TaskManager.

4. After 2-3 min's this task should be closed automatically. Now you can start WinCC flexible again as usual."

If this helps not, checkout this FAQ:
http://support.automation.siemens.com/WW/view/en/29420407