On two Windows 7 Pro computers I noticed that with the TeamViewer client running the following code stops working.

var wordProcess = Process.GetProcessesByName("winword")
    .FirstOrDefault(process => process.MainWindowTitle.Contains(documentName));

Setting a breakpoint and inspecting single running WINWORD process reveals that Process.MainWindowTitle property is blank most of the times. While WinWord windows taskbar icon clearly shows the title.

Exiting TeamViewer restores the things back to normal: Process.MainWindowTitle every time becomes properly populated.

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Tested with:
TeamViewer 9 ver. 9.0.27339, set for unattended access
MS Word 2007