The best information I have is that 'Trustedinstaller' is a genuine Windows service which is partly responsible for the correct installation of Windows updates -
However it can get corrupted and the first line of attack is to run SFC /scannow. To do this, open the command prompt as administrator. You will find it in 'Start - All programs - Accessories'. Right click on it there and choose 'Run as Administrator'. You will get a black window with white text, type SFC /SCANNOW at the prompt, note the space between 'SFC' and '/SCANNOW', and let it run. this can take a fair amount of time, upwards of an hour or more, but let it finish and see if your problem is resolved after you re-boot your computer.
If this doesn't solve your problem I would do a system restore - 'Start - Control panel - Recovery' - and follow the prompts. Your system should have created a restore point before it installed your 'long overdue update', use that one.
Once you have done the restore you will need to re-install the updates. I would suggest you set your updates to 'Notify' and install them say five at a time doing a re-boot after each batch. If one of them creates a problem it is then much easier to establish which one it is !
MS release updates on the second Tuesday of each month - for the future try installing them on a monthly basis !
PS _ Welcome to BC !
Edited by Chris Cosgrove, 28 May 2015 - 05:49 PM.
Addition of PS