Solves the problem when you launch the application and then open the file.
To do so, follow ingasvist's user instuctions: go to Playonlinux, select Office program (Word, Excel, ...), go to Configure (do not get confused by "Configure Wine"), go to the Miscellaneous tab, and in the Command to exec before run textbox, enter: XMODIFIERS="". That solved it. Keep the keyboard entry method on IBus. Repeat for other office links.
Solves the problem when you want to open directly the file from your file browser.
Go to the files located at ~/.local/share/applications. Use a text editor to modify Office launcher files and look for the line which begins like Exec=.... Modify this line by adding env XMODIFIERS="" to it. This is what mine looks like now:
Exec= env XMODIFIERS="" /usr/share/playonlinux/playonlinux --run "Microsoft Word 2010" %F