Hello!
Such problem is take place for a rather long time.
Lync is not responding after switching layout in the keyboard via hotkeys. It hangs up and then stopped when i try to bring him to life.
Note, that this occures only when switching VIA HOTKEYS, that can be set in language applet in control panel (Ctrl-1, Ctrl-2, Ctrl-3, etc). When switching with standard Ctrl-Shift/Alt-Shift all is okay. Take this into account.
Lync version: MS Lync 2013 (15.0.4517.1504) MSO (15.0.4535.1002)
OS Name: Microsoft Windows 7 EnterpriseOS Version: 6.1.7601 Service Pack 1 Build 7601