I have found an issue with the installation of SharePoint 2010 December 2011 Cumulative Update. If you are seeing the following error in you Application Log:
Product: Microsoft Shared Components - Update 'Hotfix for Microsoft Office Server (KB2597014)' could not be installed. Error code 1603. Additional information is available in the log file C:\Users\??\AppData\Local\Temp\osrv-x-none_MSPLOG.LOG.
Open the file and if you search for return value 3 you will find the actual error message just above the return code. In my situation the error was:
MSI (s) (04:18) [12:33:42:190]: Executing op: End(Checksum=0,ProgressTotalHDWord=0,ProgressTotalLDWord=9722923)
MSI (s) (04:18) [12:33:42:425]: Assembly Error:The process cannot access the file because it is being used by another process.
MSI (s) (04:18) [12:33:42:425]: Note: 1: 1935 2: {E3DD2806-A5AB-43D8-AE84-DFAF878F579C} 3: 0x80070020 4: IAssemblyCacheItem 5: Commit 6: Microsoft.Office.Server.FilterControls,fileVersion="14.0.6108.5000",version="14.0.0.0000000",culture="neutral",publicKeyToken="71E9BCE111E9429C",processorArchitecture="MSIL"
MSI (s) (04:18) [12:33:42:425]: Note: 1: 2205 2: 3: Error
MSI (s) (04:18) [12:33:42:425]: Note: 1: 2228 2: 3: Error 4: SELECT `Message` FROM `Error` WHERE `Error` = 1935
MSI (s) (04:18) [12:33:42:428]: Note: 1: 2205 2: 3: Error
MSI (s) (04:18) [12:33:42:428]: Note: 1: 2228 2: 3: Error 4: SELECT `Message` FROM `Error` WHERE `Error` = 1709
MSI (s) (04:18) [12:33:42:428]: Product: Microsoft Shared Components -- Error 1935. An error occurred during the installation of assembly 'Microsoft.Office.Server.FilterControls,fileVersion="14.0.6108.5000",version="14.0.0.0000000",culture="neutral",publicKeyToken="71E9BCE111E9429C",processorArchitecture="MSIL"'. Please refer to Help and Support for more information. HRESULT: 0x80070020. assembly interface: IAssemblyCacheItem, function: Commit, component: {E3DD2806-A5AB-43D8-AE84-DFAF878F579C}
A simple reboot and re-run of the install resolved the issue.
I am going to do some additional testing to see if I can establish why this requires a restart / re-run.