Please be aware that after installing KB3178690: security update for Microsoft Excel 2010, you might experience Excel freezing during calculations.
In the company we work for, we experienced this issue on multiple Remote Desktop Session hosts that were running 32-bit version of Excel 2010. (x86)
After removing KB3178690, Excel worked fine again. A reboot was not necessary on our servers to complete the patch removal process. (both Windows 2012 R2 and Windows 2008 R2)
On the support article of Microsoft KB3178690, Microsoft states the following in the known issues section:
After you install this security update, Excel 2010 may crash or hang (stop responding or freeze) when calculations are performed in a workbook. The calculations may be triggered either by code or by user interaction.
Microsoft is researching this problem and will post more information in this article when the information becomes available.
In the meantime, we have declined the patch on our WSUS server to prevent the update from reinstalling automatically.