I had same problem.

Before installing update pres Ctrl-Alt-Delete at same time and closes WebsiteX5.exe in memory. After closing down in memory , then install update, works to me.

succes!

Jan

If ctrl alt del does not work try :

Mayby Website x5 did not close correctly. And it is still in memory, open up your taskmanager, remove all websitex5.exe in process tab. Then try again. Do this during update (directly after the update program has closed X5)

Opening taskmanager depend on you OS. ctrl and shift and escape is the most common keys (all together)
Or
Type in at start -> run -> taskmgr and enter

to Jan, niet alle OS is ctrl alt del (meeste niet meer) vandaar even zo...