Consider the following scenario:
When you click a link in Excel to another Office document, you may receive an error saying "Cannot locate the internet server or proxy server." Using Bing, your search brings you to KB Article 218153 (http://support.microsoft.com/kb/218153) which tells you to add a registry key with a value of ForceShellExecute. However after doing this, you may find that when you click the link to another Office document in Excel, you get a spinner that does nothing. It doesn't open the document, it doesn't give an error - nothing happens.
A fix had previously been released for Excel 2007 (http://support.microsoft.com/kb/2596545). But only recently was a fix released for Excel 2010 workbooks "Descriptionof the Excel 2010 hotfix package (x86 Excel-x-none.msp, x64 Excel-x-none.msp): February 28, 2012" (http://support.microsoft.com/kb/2597142).
The 32-bit version of this patch is: Excel2010-kb2597142-fullfile-x86-glb.exeThe 64-bit version of this patch is: Excel2010-kb2597142-fullfile-x64-glb.exe
Upon a successful installation, your version of EXCEL.EXE will be updated to build 14.0.6117.5000.